Not sure about tightening anything but I would first make sure you have nothing placed in there that is rattling (been there, done that). If that isn't the problem, I would then try to find the exact place where the rattling is occurring and place foam weather stripping (they seel it in grey and black) in that area, so long as it does not interfere with the proper opening and closure of the box. I had to do that in a car I once owned.
