If you're stripping their heads, the holes are likely too small or you haven't waxed the screws.
Or, it could be that you've got shite for a screwdriver. Unclench $4 at Sears and buy a nice #1 phillips.
Also, those screws don't hold the tuners in. They're just there for anti-rotation purposes. They don't need to be tighter than dammit. Open the hole to 1/16", and wax the screw before you drive it in. Beeswax is best, but even a crayon or a candle is better than nothing. Stay away from soap.
Keep in mind that even the better tuners come with junk screws, so you gotta treat them with kid gloves. Best bet is to find a supplier of something a little more robust and go with that, but if you follow the advice above, you can usually use what the OEM ships with the things.