I work at two places, and it depends on the place. In my line of work, "mistakes" happen all the time (it's part of the experimental/scientific process
).
At one work place, I would NOT tell my boss, unless it concerned her. She doesn't care or want to know - just wants a robot to get the job down and really couldn't care less about her employees lifestyle, etc. I like everyone else I work with - and have good communication with them.
At the other work place, I would probably mention it, if it came up. I never feel like I have to hide anything and I have a great relationship with my boss and colleagues. I really value that!