I don't use individual tape cases, but I use one the tape holder things for Sega carts, which I have hanging on my man-cave wall. Sega Master System & Genesis games are a perfect fit for these things.
It's got a little Sega Master System (those are the ones with the ghetto self-made labels because Sega was too cheap to make spine labels on Master System games), a little Sega Genesis, and a some actual cassettes (mostly 80s stuff). And I do have boxes for a lot of these games, but their in a box somewhere, this was just more convenient for actual playing.