There are 2 main tools to snap objects to 90 degrees.Firstly, there is the orthogonal lock. This allows you to draw, for example, lines that are 100% horizontal or 100% vertical.
Secondly, there is Snap to Rotation. Using this, you can rotate an object so that it only rotates in multiples of 15 degrees. You can change this multiple in the Options menu -> Snap -> Snap Defaults.
I think the 2nd option may give you what you are specifically asking for.