You work at a big name store. The Barber shop and hole-in-the-wall pizza parlor I go to don't have all of those fancy gadgets.
Anyone who wants to make it in a small business needs to know their math. Also any sort of craftsman needs to do math when measuring their work and compensating for the effect of their tools.
This is true for now, but it's getting easier and cheaper to get such fancy gadgets, and the general path such technology takes is that they start getting included in the 'base model' registers as standard after a while.
The largest companies I've worked for never had more than 50 people. It's usually been less than 30. Stuff like a mom-and-pop retail store might have less than 10 with a "help wanted" sign taped to the door.
There will always be
some space for cashiers who do more than the bare minimum of work, for actual waiters/waitresses, etc.
The thing is, it's going to be more and more of a luxury service, and automated self-serve is increasingly the baseline. We're already seeing this with some fastfood places who have you order at a touch-screen kiosk instead of the register, and box stores like Walmart that now have more automated self-checkouts than traditional cash registers.
The role is never going to completely disappear, like the lift attendant, but unless we do away with crap like minimum wage laws, it'll probably become an increasingly rare thing offered only to those with disabilities and at luxury establishments.