It think it's hard to quantify, but I would say it will help. Think of it like this - the ink goes into your skin. When the sun hits your skin, it causes the ink to fade, just like the sun fades everything it touches. My house was built in 2007. The floors exposed to the sun are much lighter than the floors that never get sunlight. So the more sun your tattoos get, the more they will fade.
Given what we know about the sun today, I would not be out tanning for any reason, but if you do tan, I would rethink getting tattoos in visible areas.