Don't let the internet "cloud" come between you and your customers.
They'll be shocked and you'll be annoyed when it slows down or goes down due to issues beyond your control. -Imagine not even being able to ring items up or accept payment. You might as well be using a shoe box for a cash register!
Funny thing about clouds...
Going wireless or being internet dependent introduces more moving parts and vulnerabilities.
These can cause a system to slow down or go down, due to things beyond anyone's control.
Back in 2014 Google was making about $658 per SECOND off the internet. It's way more today. Imagine what downtime costs them and what they would do to prevent it if they could.
Go search "Google outage". There are entire sites dedicated to tracking their down times, many have occurred since 2014. Some of these sites even suggest games to play while you wait for Google to come back up. Here is a one that is a bit more serious:
Now imagine it's your check out lanes that are down. There is no game in the world that will placate a customer standing across the checkout counter from you, waiting to part with their hard earned money, so they can leave with their purchase.
Google doesn't have a choice, they are an internet company. Their programs and data are kept where their products are, and yours should be too. -It's been said that success in retail doesn't come from doing one thing right, it comes from not doing hundreds of little things wrong. If you are still considering a cloud based point of sale "slow downs and go downs" are not a little thing.