The suprise should be that it's "only" 92 degrees! Wait until you hit the net corner (94 degrees), and the one after that which will be 88 degrees!
If the framers did a bang-on job and gave you a true 90-degree inside corner, here's what usually happens. The drywall. The board are hung, you're still at 90. Then they load up the corner joints with tape and mud. Those three layers will build out the corner by a tad, theu "opening up" the angle so it is greater than 90 degrees.
Consider the reverse on an outside corner...framing and drywall are primo, at 90 degrees. Then after the corner is built up with mud, the angle is decreased to less than 90.
Outside corners always have to be mitered, but you could consider coping the inside corners. Coping allows a few degrees of wiggle room either way and doesn't tend to open up as inside miters do when the wood moves with the seasonal changes.
If all else fails, it's nice to cut two boards, each about 3' long or so, with a true 45 degree angle each. Slide them in to each corner and you'll see if 1) it fits just right, 2) you need to shave a bit off the heel, 3) you need to shave a bit off the toe. Make the appropriate adjustments on your saw when you cut the real stock.
What kind of trim are you installing? Base? Crown? Both?
I'd advise you not to cut any crown until you've read up a bit more on the subject. It'll save you a few wasted board-feet of material.