Depends on the kind of store: if it’s a place that sells necessities – ie. a grocery store, a clothing store, maybe a pet store – it’s probably all right. Say someone direly needs food or clothing or supplies for their animals, then think of the analogy of pulling the ox out of the ditch, which Christ gives to the Pharisees when they start snitting about the hungry Apostles helping themselves to some grain on the Sabbath. If it’s something not a necessity – a video store, a book store, etc – it’s more of a problem. Depending on what state you’re in, there are some states that have made it at least inadvisable (if not illegal) for an employer to insist that a worker come in to work on a day that the worker’s faith sets aside as holy.