java script rounding to nearest 10

I have a form that needs to multiply two fields and then raound the answer to the nearest ten.

Below is what I have, can someone please tell me what I am missing

function DoubleRound(nDec, nValue) {
// Rounding function - round nValue to nDec decimal places
// use a double round to eliminate rounding error or Math.round
var nRound = Math.round(nValue / Math.pow(10, -nDec + 1)) * Math.pow(10, -nDec + 1)
return Math.round(nValue / Math.pow(10, -nDec)) * Math.pow(10, -nDec);
}

var u1= this.getField("TAXABLEVALUEOTHERPROPERTY").value;
var a1 = this.getField("RATIOOTHERPROPERTY").value;
event.value = ""; // default result if no divisor
if(Number(TAXABLEVALUEOTHERPROPERTY) != 0) {
// divisor not zero
var nResult = TAXABLEVALUEOTHERPROPERTY * RATIOOTHERPROPERTY; // compute division
nResult = DoubleRound(-1, nResult); // round to nearest 10
}