you should wear slacks a button up and flats or heels(less than 4 inches). you should remember the name of the person who is interviewing you, shake his/her hand and remember to smile and thank him/her for their time.
Cielo2152 is right. Dress nicely. You only get one chance to make a first impression. Show up no LESS then 10 minutes early.
They may in a round about way try to find out if you've handled money before. If you have fine if not tell them you worked in the school bookstore, ringing in school related items & apparel. If you want you can also claim that at the end of the shift you had to balance the bank. You won't have to do that @ the home-depot, but it sounds good.