Yes, if you overpay then you go back in and get the change back. If I give the cashier a twenty, but only pump $10 worth, then I get $10 back from them. Most pe

Yes, if you overpay then you go back in and get the change back. If I give the cashier a twenty, but only pump $10 worth, then I get $10 back from them. Most people are pretty good at estimating it though, so generally the people that pay in cash will just leave the few dozen cents they didn't use.