I asked my wife. (ok, I am a wuss)
She says "till" is wrong.
until and ( 'til or til -bordering on optional)
I wouldn't bet against her.
Now of course that is not to say that till is not common, but the Human English Language Compendium has spoken. "The staff of knowledge slams hard onto the marble floor! Mortals scuttle away into the corners and under the tables and hide."
"Thus it was spake, and of course was.