We're not even sure what system the OP is referring to, but certain POS systems that operate on a 24x7 basis will have a suspense account. In these cases, a suspense account is typically a very, very short term AR account that will be paid in a matter of hours.
Case in point is a 24x7 diner. If the close of business day occurs at midnight and there is still someone with an open ticket, that ticket is accounted in sales, but not in payments received. But since the payment is coming in the next hour or so, it is simply 'suspended' from one day to the next. The next business day will have a payment, but no sale, so the other side of the entry is suspense vs sales.