Is it legal to leave money and take what you want?

In some movies, characters will grab what they want at a convenience store and throw a twenty dollar bill at the counter to cover the costs. I was just curious if this was a real thing that could be done? Not that I would ever do it because it’s an asshole move but if it’s something real that people do. My father works as a district manager for Circle K and to my understanding the whole reason behind checkout is to keep inventory and track the money going in and out.