The store I managed had a suspend/recall. Cart full of groceries only to realize you left your wallet (at home, in the car, whatever) suspend the transaction and print a slip with a barcode on it. Move the cart out of the way and take the next customer. The customer comes back and scans the slip at any register to recall the transaction, pay and collect their cart and leave without having to hold up lines/etc... Was a nice convenience many appreciated.