getting perfect rotation values

Hi all,

I am spawning room modules as instanced meshes via blueprint, their transform consists of a grid position and a rotation that is always in 90 degree increments. When the modules get placed in the world their rotation values are always slightly off (90.0008, 89.9997 etc) due to the magic happening when the rotators are made. In most cases this does not bother me, but I need the placement of all modules to be perfect to avoid visible seams in walls and so on.

So my question is, how can I avoid getting values that are slightly off or implement means to set them correctly? I searched before and I did not find a solution, so I would appreciate the help