What percentage are you looking for?
Your tax rate. Or since we are looking at calculating how much you take home each pay period, we'd need to know what percentages are being withheld for you taxes (fed income, state income, SS, etc), and since you have insurance being withheld, how much is being withheld. Without knowing all this, we won't be able to help calculate your take home figures.
However, I can give you a rough idea with rounded figures. Bumping your contributions up to 10% would be roughly another $100. However, your take home pay would only decrease by about $75 (assuming 25% tax bracket, no state taxes, and your withholding is set up efficiently), because you aren't paying tax on that $100