My local grocery store does that automatically—the register rings items up at the full price and then applies all the discounts at the very end while you're wai

My local grocery store does that automatically—the register rings items up at the full price and then applies all the discounts at the very end while you're waiting for the card reader to be ready. And it seems to do it intentionally slowly, about two line items per second, so that it takes exactly the right amount of time to be sure you notice it without getting annoyed at having to wait.