I just tell the cashier's I forgot my card. They just grab one off the stack and scan it.
This, of course, depends where you are. Randalls requires the card/phone number and the cashier won't even prompt you for it; you have to type in the number on the pinpad or hand them your card before paying.
I recently moved away from central TX where HEB is prevalent and that's one of the things I miss the most- they don't use any of this card nonsense and treat their employees well. Up here I'm stuck with Kroger and Walmart.
Of course, I'd prefer not to provide a phone number at all, but some of the local businesses (especially hair salons, for some reason) get downright hostile when I try to explain my preference. It's like it's completely unheard of to not hand your phone number out to strangers. This gives me a way to "relent" without causing a scene.