Tools > Options > Ruler > Nudge and set the increments you want.
You might like to try Nudge: 10 px, Super nudge 2 (i.e. 20 px) and Micro nudge 10 (i.e. 1 px).
Then, to move 1 pixel you would use Ctrl-Arrow, 10 pixels would be Arrow key alone and 20 pixels would be Shift-Arrow. Experiment to find settings that suit you.