[PM-34223] discounts rounding bug fix (#19811)

libs/pricing/src/components/cart-summary/cart-summary.component.spec.ts

@@ -537,6 +537,29 @@ describe("CartSummaryComponent", () => {
       ).toContain("-$10.00");
     });
 
+    it("should compute total consistent with displayed rounded line items when chained discounts produce fractional cents", () => {
+      // Reproduces: 1x $47.88 seat with 20% off → $10 flat → 5% off, tax $2.15
+      // Raw math: 47.88 - 9.576 - 10 - 1.4152 + 2.15 = 29.0388 → $29.04 (wrong)
+      // Rounded: 47.88 - 9.58 - 10 - 1.42 + 2.15 = 29.03 (correct)
+      const cart: Cart = {
+        passwordManager: {
+          seats: { quantity: 1, translationKey: "members", cost: 47.88 },
+        },
+        cadence: "annually",
+        estimatedTax: 2.15,
+        discounts: [
+          { type: DiscountTypes.PercentOff, value: 20 },
+          { type: DiscountTypes.AmountOff, value: 10 },
+          { type: DiscountTypes.PercentOff, value: 5 },
+        ],
+      };
+      fixture.componentRef.setInput("cart", cart);
+      fixture.detectChanges();
+
+      const bottomTotal = fixture.debugElement.query(By.css("[data-testid='final-total']"));
+      expect(bottomTotal.nativeElement.textContent).toContain("$29.03");
+    });
+
     it("should apply cascading subtotal when multiple percent-off discounts are stacked", () => {
       // Arrange
       const cartWithStackedPercents: Cart = {

libs/pricing/src/types/discount.spec.ts

@@ -34,6 +34,30 @@ describe("getAmount", () => {
       const discount: Discount = { type: DiscountTypes.PercentOff, value: 100 };
       expect(getAmount(discount, 200)).toBe(200);
     });
+
+    it("should round result to 2 decimal places when percent produces fractional cents", () => {
+      const discount: Discount = { type: DiscountTypes.PercentOff, value: 20 };
+      // 20% of $47.88 = $9.576 → rounds to $9.58
+      expect(getAmount(discount, 47.88)).toBe(9.58);
+    });
+
+    it("should round result when applied to a running subtotal with fractional cents", () => {
+      const discount: Discount = { type: DiscountTypes.PercentOff, value: 5 };
+      // 5% of $28.304 = $1.4152 → rounds to $1.42
+      expect(getAmount(discount, 28.304)).toBe(1.42);
+    });
+
+    it("should round half-cent up", () => {
+      const discount: Discount = { type: DiscountTypes.PercentOff, value: 50 };
+      // 50% of $0.01 = $0.005 → rounds to $0.01
+      expect(getAmount(discount, 0.01)).toBe(0.01);
+    });
+
+    it("should round down when fractional cent is less than half", () => {
+      const discount: Discount = { type: DiscountTypes.PercentOff, value: 20 };
+      // 20% of $47.82 = $9.564 → rounds down to $9.56
+      expect(getAmount(discount, 47.82)).toBe(9.56);
+    });
   });
 
   describe("AmountOff", () => {

libs/pricing/src/types/discount.ts

@@ -23,7 +23,7 @@ export const getAmount = (discount: Discount, baseAmount: number): number => {
   switch (discount.type) {
     case DiscountTypes.PercentOff: {
       const percentage = discount.value < 1 ? discount.value : discount.value / 100;
-      return baseAmount * percentage;
+      return Math.round(baseAmount * percentage * 100) / 100;
     }
     case DiscountTypes.AmountOff:
       return discount.value;