In this day and age the technology should be there to push your cart or bag thru a conveyor scanner andit tallies everything instantaneously without having to take anything out. Just ring everything up, insert card, and go.
"Futurists" sold that fiction to several large retailers decades ago, with Walmart being the biggest one.
Walmart spent a fortune chasing it and it never came through. It was predicated on RFID tags being attached to every item. The cost of the tags, the cost of affixing them to every item, and of course, dealing with theft from switching them or removing them made even Walmart finally give it up.