I can't speak for cesisco, but in my case Pixel Rounding doesn't make any difference.
I suspect it's an issue with the graphics card, or something similar, as opposed to something related to a specific capx. My Monkey on a Unicycle game in the arcade, for example, shows seams on my computer clearly, regardless of whether I'm using Chrome, Firefox, or IE:
<img src="http://imageshack.us/a/img803/3518/moauseams.png" border="0" />
Not only that, but it blurs things significantly.
Trying this on another computer gives different results, with a sharper image and no seams.