A picture would be worth a thousand words... I think we are all amazed that it was never taped and textured. Can you take pics?
If you bought the sheet rock mud without the tape you might be able to fill the seam if they are tight, but it'll crack the next time the temperature changes in the house.
But taping and texturing is a fine art.... We hired it done because it's hard to do well, and an enormous mess.
I'm OK with doing a slapdash job. I shouldn't be, but I can't afford the time or materials for much more...especially when it's likely to be redone soon. I'm about half tempted to just do it with putty or something.
*sigh*