How sweet of grandma to be thinking of you!
I am afraid 5 tiger barbs alone in a 10 gal is asking for trouble. They are very active fish and really need at least a 20 gal tank.
Maybe your grandma would let you return them for something else? If you are stuck with them, offer lots of hiding spots such as fake plants, so a fish can retreat from all the activity and possible aggression if needed.