Since I'm still a pretty new quilter, I allow myself a LOT of leeway!
I use the lowest common denominator approach where everything gets trimmed down to the smallest block and sashing makes up the difference. But so far I haven't made blocks that had points or anything that would really show the block had been trimmed.
Plus I tell myself there's a certain amount of charm in a slightly wonky quilt. Though honestly I prefer things to line up, I'm just not all that skilled yet. My first quilt has blocks that are probably a half-inch off - thankfully I've gotten a LOT better! LOL