Fucking self-scan tills!
My nearby Sainsburys has a habit of closing all the operator tills after about 9PM.
I refuse to use the self-scan ones and always ask for an assistant.
Keeps spotty teens off the streets, and doesn't give me a pocketful of shrapnel. Sainsburys tills do not dispense 50p pieces. I once got 4 x 20p plus 9 x 2p coins as change. That was the last time I used one.
It's the only way to be sure.