I don't think it's ok to do something wrong on purpose, regardless of whether people find out or not.
Firstly, we never know the true repercussions of our actions. It might seem like no-one was hurt or inconvenienced by a small infraction that never gets found out about... Take shoplifting for example.
You might steal something from a store, thinking that they'd never find out and that no-one would get in trouble. But after the store closes, they audit all their items, realize something is missing, and then the security guard might lose his job for not preventing it, or the staff members might get accused of stealing the item themselves...
Also, even if you do get away with doing something wrong, it will only make it easier for you to justify doing it again, and again... And eventually there will be a repercussion.
Better never to start down that path in the first place.
Finally, if you believe in karma, then the theory goes that every wrongdoing you perform, whether discovered by others or not, will come back to bite you in the ass eventually.