We all had that teacher who warned us never to use double negatives. Never say or write, “I don’t have no red shoes.” In fact, if you say that sentence with the emphasis on the word “no,” you might be saying, “I don’t have no red shoes; I have some red shoes.”
I don’t recall ever being warned about triple negatives, but they exist: “I wouldn’t like to say that I would never not wear a bikini.” Granted, that sentence is convoluted. It would be preferable to say, “I might possibly wear a bikini,” but the triple negative version is still grammatical.
Most double negatives we see are, in fact, ungrammatical. “I don’t have nothing to tell you” likely doesn’t mean “I have something to tell you.” It’s an ungrammatical way to say “I have nothing to tell you.” Sometimes, however, many of us talk that way when among people who know us very well. They are aware we know better but understand we are using a double negative in an attempt (albeit feeble) to be funny.