Serial Killer Couple Movie

Two people, man and woman, become connected via a bdsm relationship as coworkers. They then begin to travel across America, eventually killing people for fun. They get off on it. They hitchhike near the end and two young women pick them up in their rv. Eventually they make the women stop the rv. They kill them and move on with their killing spree. Unknown to them, one of the girls they thought they killed survived. She tracks the couple down, hides in the room and kills them both

The Billie Holiday song

"You Can't Take that Away from Me"

Plays once or twice in the film.

I've seen the film but failed to write the title down.