It's a sound those of us who grew up 'back-in-the-day' will never forget.

The 'Ka-ching' of the old cash register.

Maybe we were buying some bubble gum. Maybe it was baseball cards. Perhaps it was a comic book. Up to the counter we'd go, plop down out .25 and wait to here it. The lady (it seemed to be always a lady) would push down a couple magic keys, pull a lever and then...

Ka-ching!

Well, according to the Associated Press, those days are just about gone.

(AP) - Ka-ching! It's a sound we're hearing less and less.

Stores across the country are ditching cash registers. Instead, salespeople - and even shoppers themselves - ring up sales on smartphones and tablet computers.

The Urban Outfitters clothing chain ordered its last traditional register last fall. And Wal-Mart is testing a "Scan & Go" app that lets customers scan their items as they shop.