This is a great scene for the readers to think about. We certainly know that after this chapter, Tom goes to Wilson and makes sure to tell him that Gatsby was driving the car, but the question is "does he really believe that? or is he covering for Daisy." By doing this, he essentially ensures that Wilson will exact his revenge on Gatsby, and he does just that when he kills Gatsby and himself in chapter 8. This puts to a complete end any and all of the the conflicts in Tom's life -- the threat to his marriage is gone and all suspicion that may have fallen on Daisy is put to rest. There is no one left to question what happened that fateful night. With all that said, we don't know what was actually said in the kitchen that night, but I think Daisy and Tom's behavior in chapter 8 and 9 suggests that Tom did learn the whole truth that night, and preserving his status in society, and along with that,his society marriage to Daisy was more important than truth and justice. Daisy had already rejected the idea of being with Gatsby when she refused to say that she never loved Tom back at the hotel scene, so her confessing to Tom makes sense. She is doing what she needs to in order to preserve her place in society. She will do whatever it takes. The fact that Tom and Daisy don't even acknowledge Gatsby's death is evidence of where Daisy's priorities are at the end of the novel. She is more attached to Tom than ever. Their shallow carelessness is what appalls Nick, and us, by the end of the novel.