When I was little, I worked part-time at the Coop. I wasn't able to drive a till until I was 16, but I did it all. Shelf-stacking, loading the cages for the shelf-stackers), tutting at their poor attempts at facing up displays and rotating the stock, and every Saturday afternoon I got to put away all the veg and clean up all the displays, getting rid of all the mushy stuff that had fallen down the back.
Actually, I have fond memories of that, because it was always the downward slope from 3pm on Saturday afternoon (I'm old enough that supermarkets still closed at 5pm).
I was also the store detective, though I mostly let people get away with it. Old ladies stealing tins of salmon for their cats was the main thing (it got so bad they had to sell it from behind the cigarette counter). I was also the only person trusted by the manager with access to the booze and cigarettes storeroom. To be fair, I never nicked anything, but I did once drop twelve bottles of whisky.