Can you trade nintendo ds games in at blockbuster ?

I work at a Blockbuster and we do trade games but you only get store credit, never cash. Since its store credit its usually more than what you'd get at gaming store and definitely more than at a pawnshop. The amount varies on how long the game has been out or how popular it is. For example the NDS Pokemon White it was $15. For Wii Epic Mickey $17. At the pawnshops in our area they would only give $5-$8.