You don't really need processing power for a register. It just needs to run an OS and the corporate software on top of it which shouldn't be that demanding. Mostly just communicating with servers, processing basic I/O, finding totals, basic stuff. Ipads just don't have good scalability (No possibility of hardware upgrades)and are a poor investment for this type of scenario just like those god damned "myDevices". They have limited IO options, are proprietary mobile hardware, and are Apple products so you know they suck compared to Android competition. In fact, they might actually go down that road since Apple is "trendy"! You would probably want a secure option from an established company in this industry especially because you want max up time with max longevity. Apple only leads in marketing.
Regardless I hope they install self checkouts in the local store, they have so many registers but even when its busy they don't even have enough people to fill half them up. More than once I have said "Fuck it, I'll go to walmart tomorrow" because their were lines when I got off work. They should just do what walmart has and use self checkout as a force multiplier. I wouldn't have to have the register supervisor trying to sell me a redcard so she can get a bonus off my back either. The less social contact the better!