I think it was a vintage "items" shop - home, houseware, kitchen, etc. - not clothing, which I do. I remember thinking how cool, but tricky if you have a wide price range. I could see buyers purchasing two really low-priced items in order to get a good discount on the third, higher priced item. Still . . . it's a good promotional feature.
Guess I've never figured out how, if it's even possible, to make changes in the check out.