I tend to use my scopes highest magnification setting to zero and shoot at all ranges beyond about 100 yards. At ranges less than 100 yards I use the lowest magnification. I NEVER touch anything else. Parallax is is only an issue at longer ranges. I keep the scope on the lowest setting while hunting, if a close shot comes up parallax just isn't an issue inside of 100 yards. If a longer shot presents its self there will almost always be time to change the scopes settings, not often the case if you have scope set on 5X-12X and a 30 yard shot comes up suddenly.
Also, even with very good scopes the point of impact may change slightly as the magnification is changed. Just using the most and least magnification removes a lot of possible variables.