I've seen some grocery stores with double grocery belts, so the cashier can start checking out the next customer while the first one is finishing payment, they

I've seen some grocery stores with double grocery belts, so the cashier can start checking out the next customer while the first one is finishing payment, they just sweep a divider over so the groceries go down the next belt. This was well before chip-and-pin, they probably did because of the slowness of writing checks. Though maybe this is all moot with self-checkout since the store doesn't really care that much if it takes you a bit longer to check out. Especially if they can show you ads while you wait.