If no state income tax was withheld from the interest you received, leave boxes 15, 16, and 17 empty in TurboTax. (The entry screen might not show the box number for box 16. It just says "State ID number.") Or go back to the screen that asks about uncommon situations and uncheck the box that says "State income taxes were withheld on this interest." Then it won't ask you about boxes 15, 16, and 17. But entering zero in box 17 should accomplish the same thing, so you could do that too.
