So long as your water is good, go for it.
Remember though....tangs are extremely susceptible to white spot (Ich). Make sure you get a fat healthy one and watch it feed at the store. Personally, I would ask them to hold it for a week before you take it home.
Ideally it should be quarantined, but that is your choice.
Acclimate it slowly, in the dark. Add it to the tank in the dark.
Tangs like to hide in rock work to sleep, so make sure there are spaces for it to do so.
Purchase some of the food the store uses as well as getting some sheets of Nori, or seaweed to supplement its diet with. They are all vegetarian and need vegetable matter in their diet.
Finally, choose an easy to keep tang, such as a yellow or purple, a chevron or scopas or maybe a naso. Regals are ok, but powder browns powder blue and clowns are really suceptible to ich.
Good luck,
Paul.