Yes. This is completely OK. I have heard rumors that you have to rank at least one program (which I don't think is true, but you get 20 ranks with your registration fee so no reason not to throw a name in there).
You've got one week to do it by the regular deadline and until 2/22/2017 to register (which will cost you another $50).
http://www.nrmp.org/residency/main-match-events/