The keyboard of a point of sale system in a shop is generally in a dirty environment and shared with many people. People will often work the keyboard while eating and some may have used it after blowing their noses. As food build up inside the keyboard, it makes an excellent environment for germs to spread. So the odds are that it is incredibly dirty and full of bugs. So regularly I suggest that you give it a clean.
This is how I do it.
Before I start to clean the keyboard, I turn off the computer. I find this quicker then disconnecting the keyboard.
On the keyboard, I find a sticky note is great for running down the tracks to pick up the loose debris that collects there as it sticks to the glue. So keyboards need a few sticky notes. Sometimes a toothpick is handy here for bigger stuff. Then I use a cotton swab into some rubbing alcohol to get into these tracks too. Now I may need another sticky note to run through again.
Now I use a cloth with only a touch of the rubbing alcohol and wipe the surface. If a spot does not go away, the toothpick is useful to remove the spot too.
Now wipe with a dry cloth. Do not leave the keyboard moist.
Cleaning a computer keyboard is not just about looking good but also about good personal hygiene