There are some businesses that keep track of exact change used and gave. If the worker had already pressed the 5€ option, then if they were to give you a dollar rather than 3 coins, then the tills 'wouldn't add up' and that's a write up. Now I know the total is correct but the bills and change are sometimes seen as 2 seperate entities and very anal companies care about that. It's ridiculous and I hate it.