ffmpeg accurate timing with video/audio extraction

I am trying to extract very small pieces of a .mp4 file using ffmpeg.

I am using ffmpeg at the command line for this.

I am using win32 static build, build on 3/14/2014.
(Does ffmpeg for linux work better than ffmpeg for windows?)

An example extract command is -
ffmpeg -ss 20.05 -i robert2.mp4 -t 0.1 -c copy output2.mp4

In this example I am trying to start at a position of 20.05 seconds and extract .1 seconds of video.

the problem is that ffmpeg seems to be aligning itself to certain boundaries.

So it doesn't seem to matter whether I tell it to start at 20.0 seconds or 20.5 seconds, it still seems to start at the same point.

I have also tried using frames -
ffmpeg -i robert2.mp4 -ss 14.6 -frames:v 20 output3.mp4

Using frames seems to be very accurate, but the audio and the video don't seem to sync properly.

Does anyone know how to get ffmpeg to give me very accurate small extractions?

I need to go down to < .1 second resolution.  Also, I need the audio to properly extract and sync as well.

Or is there a better command line tool for this?

I am willing to pay for a  tool (within reasonable cost) as long as I can use it at the command line and/or with scripting and as long as it is accurate and efficient.

Thanks, Kevin.