The 412 has basicly got the same Tail Rotor & drive shafts as the 212 205 & 204 (yes I know the T/R was on the other side on a 204).
People have been using the T/R to turn the rotors since the Huey entered service & they have had very few T/R failure problems.
There is nothing in the flight manual or the maintenance manual prohibiting this.
However, be gentle when you do.