Thanks for the quick suggestion.  It would work for some customers.  But with California sales tax laws, cold sandwiches take-out are not taxable, but hot sandwiches, in all cases, are taxable.  So if a customer orders both a hot and cold sandwich, this solution won't work.  Hopefully there is a product specific solution.  Otherwise, I think I'll have to use the item edit (not options>tax exempt).
Thanks again.