If possible, I try "I'm just paying cash" and that stops the questions about half the time.
When they insist, I try to work with those intrusive questions, since the questioner really has no choice but to ask them.
My name is John Cash (I pay cash for a large portion of my purchases).
My address is 79 Wistful Vista (I loved the old Fibber McGee & Molly radio show).
My city is Springfield (of course), and there really is one not that far away.
My phone number is a local area code and whatever random numbers I think of.
My email is firstname.lastname@example.org
(Steve Case was a founder of AOL).