So you all know those times when you need something from the shop, but you really couldn't be bothered to go, but you really have to. Just as much as you all know that in such circumstances you generally only take enough coins to be able to get the item. You also, I assume, are familiar with the feeling of then getting at your shop, getting your item and then being short by a few cents, and then having to return it and walk away feeling ever so very slightly like an idiot, and that everyone in the shop is looking at this poor idiot who can't afford something.