I've seen in grammar books that only parentheses end up being used within parentheses and more and more. There's actually a really funny grammar book that I can't remember the title of where the author really emphasizes this by pointing out something (and then explains further (even though it's not really necessary (but you could say that it's the only way to get the point across (yet one would expect that the one reading this would understand the complexities of parentheses (but perhaps they are reading this because they do not understand and do not care about complexities (but shouldn't anyone who actually reads about grammar care (ah well, it doesn't really matter))))))).

And that is the proper use.