I know it's not the same at all so probably not helpful but I did work experience with Boots. I was just on the shop floor, it was a really small store. It seems the people working there did the same as me ie went along with the scanner thing, updated the stock numbers, stacked shelves (that and grumbled about their pay). It was really boring and repetitive, but maybe it'd be more fun on the checkout. I did my work experience before I'd ever had a part time job and I was amazed by the amount of things that got stolen from that tiny shop.
Biggest downside to those couple of weeks was the amount of times the acetate 'out of stock' things went up my fingernails.