Scan the basket, take the cash, hand back exact change — before the queue loses patience. Real Australian notes and coins, and the real 5-cent cash rounding.
Australia withdrew the 1c and 2c coins in 1992, so cash totals round to the nearest 5 cents. Card payments don't round — they're charged to the exact cent. This game rounds only on cash, exactly like a real till.
The change itself uses the greedy method: always take the largest denomination that fits. For Australian denominations that provably gives the fewest pieces every time — verified across every 5c step up to $200 before this shipped. Not every currency has that property; ours does.
Making change is genuine mental arithmetic with instant feedback, which is why it's one of the better ways to teach money. No accounts, no purchases, nothing saved — safe to hand to a child.