diff --git a/TODO.md b/TODO.md
index 5dcf61e09b..f83e2e289b 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,7 +1,7 @@
 In-Memory Order Updater TODO
 ===
 
-- [ ] Add additional cases to item_total_updater_spec (doesn't currently account for included adjustments)
+- [x] Add additional cases to item_total_updater_spec (doesn't currently account for included adjustments)
 - [ ] Consider Sofia's recommendation to break this class into POROs to simplify testing
 - [ ] Add test coverage for `update_item_total` when line item totals change
 - [ ] Test coverage to ensure state changes aren't persisted (if someone changes current implementation)
diff --git a/core/app/models/spree/in_memory_order_updater.rb b/core/app/models/spree/in_memory_order_updater.rb
index b91f0e3037..963257bdd1 100644
--- a/core/app/models/spree/in_memory_order_updater.rb
+++ b/core/app/models/spree/in_memory_order_updater.rb
@@ -120,8 +120,9 @@ def update_adjustments(persist:)
       # It also fits the criteria for sales tax as outlined here:
       # http://www.boe.ca.gov/formspubs/pub113/
       update_promotions(persist:)
-      update_taxes
-      update_item_totals(persist:)
+      update_tax_adjustments
+      recalculate_item_totals
+      persist_changes_to_items if persist
     end
 
     # Updates the following Order total values:
@@ -163,40 +164,32 @@ def update_promotions(persist:)
       end.new(order).call
     end
 
-    def update_taxes
+    # TODO: split implementation based on 'persist'
+    def update_tax_adjustments
       Spree::Config.tax_adjuster_class.new(order).adjust!
-
-      [*line_items, *shipments].each do |item|
-        tax_adjustments = item.adjustments.select(&:tax?)
-        # Tax adjustments come in not one but *two* exciting flavours:
-        # Included & additional
-
-        # Included tax adjustments are those which are included in the price.
-        # These ones should not affect the eventual total price.
-        #
-        # Additional tax adjustments are the opposite, affecting the final total.
-        item.included_tax_total   = tax_adjustments.select(&:included?).sum(&:amount)
-        item.additional_tax_total = tax_adjustments.reject(&:included?).sum(&:amount)
-      end
     end
 
     def update_cancellations
     end
     deprecate :update_cancellations, deprecator: Spree.deprecator
 
-    def update_item_totals(persist:)
+    def recalculate_item_totals
       [*line_items, *shipments].each do |item|
-        Spree::ItemTotalUpdater.recalculate(item)
-
-        if persist && item.changed?
-          item.update_columns(
-            promo_total:          item.promo_total,
-            included_tax_total:   item.included_tax_total,
-            additional_tax_total: item.additional_tax_total,
-            adjustment_total:     item.adjustment_total,
-            updated_at:           Time.current,
-          )
-        end
+        Spree::ItemTotal.new(item).recalculate!
+      end
+    end
+
+    def persist_item_changes
+      [*line_items, *shipments].each do |item|
+        next unless item.changed?
+
+        item.update_columns(
+          promo_total:          item.promo_total,
+          included_tax_total:   item.included_tax_total,
+          additional_tax_total: item.additional_tax_total,
+          adjustment_total:     item.adjustment_total,
+          updated_at:           Time.current,
+        )
       end
     end
 
diff --git a/core/app/models/spree/item_total.rb b/core/app/models/spree/item_total.rb
index 8d13ccbeac..3ef666e39e 100644
--- a/core/app/models/spree/item_total.rb
+++ b/core/app/models/spree/item_total.rb
@@ -6,6 +6,15 @@ def initialize(item)
   end
 
   def recalculate!
+    tax_adjustments = item.adjustments.select(&:tax?)
+
+    # Included tax adjustments are those which are included in the price.
+    # These ones should not affect the eventual total price.
+    #
+    # Additional tax adjustments are the opposite, affecting the final total.
+    item.included_tax_total   = tax_adjustments.select(&:included?).sum(&:amount)
+    item.additional_tax_total = tax_adjustments.reject(&:included?).sum(&:amount)
+
     item.adjustment_total = item.adjustments.reject(&:included?).sum(&:amount)
   end
 
diff --git a/core/spec/models/spree/item_total_spec.rb b/core/spec/models/spree/item_total_spec.rb
index 9d71cf9352..1f6a2433a6 100644
--- a/core/spec/models/spree/item_total_spec.rb
+++ b/core/spec/models/spree/item_total_spec.rb
@@ -6,18 +6,46 @@
   describe "#recalculate!" do
     subject { described_class.new(item).recalculate! }
 
-    let(:item) { create :line_item, adjustments: [adjustment] }
-    let(:adjustment) { create :adjustment, amount: 19.99 }
+    let(:item) { create :line_item, adjustments: }
 
-    it "sets the adjustment total on the item" do
-      expect { subject }
-        .to change { item.adjustment_total }
-        .from(0).to(19.99)
+    let(:tax_rate) { create(:tax_rate) }
+
+    let(:arbitrary_adjustment) { create :adjustment, amount: 1, source: nil }
+    let(:included_tax_adjustment) { create :adjustment, amount: 2, source: tax_rate, included: true }
+    let(:additional_tax_adjustment) { create :adjustment, amount: 3, source: tax_rate, included: false }
+
+    context "with multiple types of adjustments" do
+      let(:adjustments) { [arbitrary_adjustment, included_tax_adjustment, additional_tax_adjustment] }
+
+      it "updates item totals" do
+        expect {
+          subject
+        }.to change(item, :adjustment_total).from(0).to(4).
+          and change { item.included_tax_total }.from(0).to(2).
+          and change { item.additional_tax_total }.from(0).to(3)
+      end
     end
 
-    it "does not factor in included adjustments" do
-      adjustment.update!(included: true)
-      expect { subject }.not_to change { item.adjustment_total }.from(0)
+    context "with only an arbitrary adjustment" do
+      let(:adjustments) { [arbitrary_adjustment] }
+
+      it "updates the adjustment total" do
+        expect {
+          subject
+        }.to change { item.adjustment_total }.from(0).to(1)
+      end
+    end
+
+    context "with only tax adjustments" do
+      let(:adjustments) { [included_tax_adjustment, additional_tax_adjustment] }
+
+      it "updates the adjustment total" do
+        expect {
+          subject
+        }.to change { item.adjustment_total }.from(0).to(3).
+          and change { item.included_tax_total }.from(0).to(2).
+          and change { item.additional_tax_total }.from(0).to(3)
+      end
     end
   end
 end