I've only ever payed for gas with the cashier twice in my life, both times because my gas card was declined, the second time happened today. I look like a total dink like I don't know what I'm doing because I do it so infrequently. So he tells me to just tell him a dollar amount and whatever doesn't get used goes back to my card. So I think of a number that should for sure fill my tank and say "$50." Sure enough, my tank fills at $40.00 and some change. I got to thinking though, what's to stop people from fucking with this dude and going "Give me one billion dollars worth of gas, please."? If you intended for your tank to be completely full, there is literally no negative consequence. At first I was thinking maybe the cashier would push back and be like, "sir, I cannot do that, give me a reasonable number," but then I thought about it and the cashier has no negative consequence of just rolling with the joke too, if they feel so inclined. But then, I thought of that you could really troll them. Like if your pump is gonna decline my card and make me come inside like it's the fucking dark ages, I'm gonna troll you because fuck you. "Give me one billion dollars worth of gas please. And don't just punch in 100, I want to see you punch that 0 key nine times! You think I won't count, but I will!"