Who sings lyrics what goes around comes from episode of True Blood?

The song "What Goes Around" in the episode of True Blood you're likely thinking of is by Justin Timberlake.

It's featured in the Season 3 premiere episode, "It's a Shame About Ray." The scene features Jason Stackhouse (Ryan Kwanten) and his girlfriend, Crystal Norris (Lindsay Pulsipher), listening to the song in her car.