Script Goes Haywire When Two Of Three Elements Return 0

So my code is supposed to retrieve three values from a flash element. Now it works fine, but when it retrieves a 0 from any of the three valuse, it goes all haywire. How could I put in a statement or command that if it returns 0, that all it will display is a 0 instead of returning "NaN"? But since all three valuse added together are supposed to equal 100% i have to run the numbers through a little bit of division and rounding after it gets the value of each one.

var techfaction = document.getElementById('tfaction');
var natfaction = document.getElementById('nfaction');
var magfaction = document.getElementById('mfaction');
retrFaction();
roundNumber();

function retrFaction()
{
var values = document.documentElement.innerHTML.match(/factiontrianglesmall.swf??.*\x26link/i)[0].match(/[0-9.]{4,9}/ig);
techfaction.innerHTML = roundNumber(values[0] / 30, 1) + '%';
natfaction.innerHTML = roundNumber(values[1] / 30, 1) + '%';
magfaction.innerHTML = roundNumber(values[2] / 30, 1) + '%';
}

function roundNumber(num, dec)
{
var result = Math.round(num*Math.pow(10,dec))/Math.pow(10,dec);
return result;
}