Rotate by exact amount?

[FlailAway]

Hi, I have a square hole in a project and the hole is rotated 22.5 degrees to miss some blades on an impeller. I cannot seem to get other than full-1-degree movements.

I do not want to have to redesign the impeller for just 1/2 a degree. When printing the missing half degree is not giving a smooth flat face for the square surfaces that then need a lot of hand filing.