Rounding to 2 decimal places ONLY

I have a form in which I am using the below custom calculation script:

// Acquire Inputs
var nA = Number(this.getField("Yes1").valueAsString);
var nB = Number(this.getField("TotalOSAudited").valueAsString);
var nSum = Number(this.getField("YesPerc1").valueAsString);

// Perform Calculation
var nSum = (nA / nB)*100;

// Assign Result to Field
event.value = nSum;

The select format category is None.  I need the calculation to round to 2 decimal places ONLY.  I have spent the last two days going cross eyed searching for the answer.  I am a newby to any sort of script.  Thanks for the help!