I know of at least one retailer here who times their cashiers, so if the customer is slow getting out their payment, it reflects badly on them. I have heard one of these cashiers mention that they like it when the customer uses a debit card, because as soon as they hit the ‘debit’ button that’s them finished, as they have no control over how long the equipment takes to process the transaction. So I always use my debit card when I shop there, because I don’t want them being scolded for the time it takes me to manage my end of the transaction.