Split discountCents across lines proportionally to each line's total, as whole cents that sum EXACTLY to
discountCents (largest-remainder apportionment). This is what keeps the cart drawer and the order summary
from disagreeing by a cent. Each line's share is clamped to its own total.
Split
discountCentsacrosslinesproportionally to each line's total, as whole cents that sum EXACTLY todiscountCents(largest-remainder apportionment). This is what keeps the cart drawer and the order summary from disagreeing by a cent. Each line's share is clamped to its own total.