The RotView addon serves
the purpose of setting fixed rotation values for each of the
right/left/front/back/top/bottom views.
Documentation
First go to User Preferences->Addons and enable the RotView addon in the
3D View category.
To change the rotation in realtime first press one of the numerical keypad
view shortcuts to switch into a view and set the rotation
value with the slider (doubleclick for keyboard input) or use the <-90
and 90-> buttons to
switch to the next multiple of 90 degrees value. Button 0 goes back to
zero rotation.
The rotation value of each of the views will be remembered when switching
into it again from
the numerical keypad.
REMARK - when first enabling the addon, when in an affected view already,
rotation will not work.
Enable the view again with
numerical keypad shortcut.
REMARK - will not work when switching view through the View menu