Two things you may have misunderstood...
1. This is not a "we do your homework" servce. Somebody may help you learn how to round your results, but nobody will just do it for you.
Anyway, to answer to the question (even though the thread is closed), you should parse the number, multiply by 100, compute the result, round it, then divide it again by 100.
var a = 234.244
var b = 51.654
var upA = a*100
var upB = b*100
var resA = Math.round((upA*3.35)) / 100 // <= 784.72
var resB = Math.round((upB*3.35)) / 100 // <= 173.04