Look up the meaning of ‘public accomodations’. By US law any business that is not a private club or a religious institution must serve all who come to its doors.
If I have perishable stock on a public retail store shelf, and you have legal tender, I can’t refuse to sell that item to you. Why would I?
No store warranty need be offered, and if the product is defective, the customer can take that issue directly up with the manufacturer, not the retailer.
Custom and/or special orders are a whole different story.
Bussinesses can and do refuse to serve customers who want “custom” services every single day.