What is the ruling on working as an accountant (cashier) in a store that sells prohibited items such as cigarettes and pork, knowing that his work is limited to accounting for the customer's purchases, and the store sells other permissible goods?

It is not permissible to sell forbidden items such as tobacco and pork, because when Allah forbids a thing, He also forbids its price, and because selling them constitutes aiding in sin. The cashier who handles sales is not permitted to sell forbidden items and sins every time he does so. His sin is no less than that of the promoter or carrier of forbidden items.