To reproduce:

1. Open Unity, create a new project and open it
2. Create Cube or other gameObject and select it
3. Rotate that gameObject with Crtl button on selected axis until 95 degrees is reached

Expected result: Value in Inspector will be 95.0
Actual result: Value in Inspector will be 90.00001

Notes:
- This issue appears on Windows and OSX
- If you rotate X axis until 554.999 or -554.999 degrees, then Y and Z axis of Rotation moves from zero value to -1.525879e-05 or 1.525879e-05. If you rotate it more until X axis reaches 630 or -630, then Y and Z axis of Rotation will return to zero value. Also, it happens with 825 or -825 values on X axis and everything fixes on 914.999 or -914.999 values.

Reproduced on Unity 5.5.5p1, 5.6.4p2, 2017.1.2p2, 2017.2.0p1, 2017.3.0b8 and 2018.1.0a3