In some stores you can tap your card before the transaction is completed, once the receipt is 'closed' the payment terminal will receive the final amount and us

In some stores you can tap your card before the transaction is completed, once the receipt is 'closed' the payment terminal will receive the final amount and use the authorized session to complete the payment. You can also simply wait for the receipt to be closed before tapping, then the terminal will show you the full amount. I - for example - use the pre-transaction tapping when buying groceries, it means I can just walk out when the last item is scanned. It is a security risk - an attacker may add some expensive item to the session - but I think I can take it, the terminal will still show the total at transaction close.