Thanks!
To answer your question, no the zoom level or scaling of the browser itself does not affect the value of the Mouse Wheel Axis. However, if I flick the mouse wheel really fast, the value printed out varies from 0.025, 0.05, 0.075, and 0.1.
My workaround is just to check if the Mouse Wheel Axis value is greater or less than 0 and then manually set the value that I use to 1 or -1. This covers all browsers and platforms I would think.