as many bags as you need to put your groceries in. I been caught too many times being short and then having to pay 10 cents a bag for the extra groceries that couldn't fit in my grocery bags.
Our store GIVES us 5 cents for each bag of our own that we use. But you'd be surprised how few people take advantage of this. I have a designated tote bag that gets washed often for bringing home the groceries, and a few plastic bags are in this bag all them time. I feel really bad if I forget this bag when I go to the store. Sometimes I just use my purse for small items. I hate taking another bag home from the store.