A little disappointing to see this one is still present in 1.5, as it really does need to be addressed. It makes clinical alignment impossible, forcing builds to be imperfect. Often people have no idea why they have join lines when they feel they have accurately rotated.
In 1.5..
Rez a sphere. Default rotation is X 0.00, Y 90.00, Z 0.00.
Now set the Z to being 180.00
As you leave the field, it will flip to showing 180.01. The object will not quite align with anything. If you type 180.00 back in to force it, it appears to hold - but selecting something else then returning to the object will show it has reset to 180.01 again.
I have Bug Reported it. Very frustrating.
Jai.