You can do the same in some stores. They put out some ripe and some unripe. Just grab a couple of each. And don’t fall for the guilt of breaking up bunches. You are allowed to do that. You don’t have to buy the whole bunch. Unless you go to a store that unnecessarily puts then in plastic containers/wraps.
And you can still rinse the banana off to get rid of any germs from inside the store if that’s the fear. It won’t damage it. But do it when you are ready to eat it otherwise if you use mild soap it can reduce the life of the banana by making the skin less protective.