Tom and Daisy didn't have a marriage based on devotion solely to each other; they both considered their own interests and desires to be of more importance than the concerns of the other. However, they considered their social standing and reputation as a couple to be of even more importance than their individual positions because they enjoyed the status and lifestyle that wealth allowed them.
In the aftermath of the car accident, their separate interests became less important than coming together to protect and preserve the lifestyle they shared. Tom never found out that Daisy had been driving, that she was the one who actually hit and killed Myrtle Wilson. As far as Tom knew, Gatsby was responsible for the accident. Daisy never told him anything else, an indication of how much she cared about Gatsby's position in her life.
Tom and Daisy came together to figure out how they could distance themselves from the unpleasantness until all was forgotten.
Daisy and Tom were sitting opposite each other at the kitchen table...He was talking intently across the table at her...Once in a while she looked up at him and nodded in agreement...There was an unmistakable air of natural intimacy about the picture, and anybody would have said that they were conspiring together.