'Checkout' is certainly not the same as 'till'. All shops used to have a till, aka a cash register, to keep the money in & get the change from. But the 'checkout' consists only partly of a till, but with the addition of a belt on which one places one's purchases from one's trolley, which are then scanned by the operator & a total sum for payment reported to the customer -- who then, unless paying by credit card, hands over the money, which is put into the till, which is a part, but only a part, of the total apparatus involved.

The whole of the area concerned -- the aisle thru which one passes to place one's purchases on the belt prior to paying one's money to be put into the till, is subsumed under the designation 'checkout'. Probably originally an American word, because the supermarket system of self-service & checking out originated there. But a very useful & comprehensive term it is indeed.

~M~