The fine was announced on Monday. The gesture happened on Saturday night after Martin hit a three-pointer with a little over 90 seconds to play in the game.
As Martin headed to the other end of the court he "Casselled" down the court: "he cupped his hands and held them just below his waist".
The gesture was made popular by former Timberwolves guard Sam Cassell, who used to do it after big shots--that was until the NBA started issuing fines to curb it.
Kevin Martin finished with 33 points in the 106-105 loss, after Jimmy Butler hit two free throws for the lead and the win, with 0.2 seconds to play.