I'm sure there must be a way during rendering but I can't seem to find it.

Show the Master track in the track view. Enable volume automation envelope and "draw" in your fade. That's one way... I admit most of the time I do this in another editor that I have where I psuedo-master the songs rendered from Reaper and comile/burn CD's. Adobe Audition. D

I use the master track way as above, View/Show Master Track(Ctrl+Alt+M) then Highlight the master track and press V on your keyboard.This will show the Volume envelope.Then go to the end of the track and click a couple of envelope points and set how you want it to fade. HTH :)

Or draw the curve you want.... I tweak my fade outs, you can too.

Thank y'all very much! I'm kinda old school I guess,,,,in my 50's,so if you can automate the master fader I'll just ride her till the end ,,,,at least the 1st time. THanks a lot guys,,,,,big help.

I haven't worked with many hardware controllers, but I know that the MCU specification uses pitch messages for their faders, thus providing 14 bit (some over 16000 positions). Endless rotaries don't even show this problem, as they use the resolution of the receiving parameter. Have only tried an MCU once (to be correct, it was a LC that days), but tried with exactly the resolution in mind. No complains here, the fades where absolutely smooth. I'd think that any controller which claims to be MCU compliant would use those 14bit. EDIT: What Dan says about the bit resolution when the fade goes towards zero is of course true, but since I use 24bit recording I am much more confident at that end. Plus I think as long as I don't fade the master I benefit from 64bit resolution. I can clearly see the joy in handling nice analog faders, but I won't trade it for the possibility to easily edit what I have done after the fact.