Jared Dmytriw broke a 2-2 tie 3:40 into the third period and Davis Koch, with his second goal of the game, scored into the empty net with 15 seconds left in the period.
Owen Hardy also scored for the Giants.
Parker Kelly scored both goals for the Raiders.
David Tendeck stopped 36 of the 38 shots he faced in net for the Giants, while Ian Scott made 23 saves in the loss.
Game 7 goes Monday evening in Prince Albert.
The winner is off to the Memorial Cup, which starts on Friday in Halifax.