Buckle, from Queensland, was two shots off the lead to start the day but a strong round was enough to pass overnight leader Paul Sheehan.
Sheehan, who had posted three consecutive sub-70 rounds, could only muster a final-round even par 72 that dropped him into a tie for second.
He was joined by Ryan Haller of Queensland and Craig Warren of New South Wales, who both carded 4-under-par 68s.
Craig Jones finished alone in fifth at 11-under 277.
Five players ended the tournament five back at 9-under par and in a tie for sixth.