I have the following code in a site I inherited. The calculation adds 3% to a transaction for ecommerce purposes. I am trying to ensure the calculation rounds only to the first two decimal places. I am a bit of a newbie. Thoughts?

<script>
function calculate() {
document.getElementById("amount").value=0;
document.getElementById("amount").value=parseFloat(document.getElementById

("payment_value").value)+parseFloat(document.getElementById("payment_value").value)*0.03;
document.getElementById("amount_show").innerHTML=parseFloat

(document.getElementById("payment_value").value)+parseFloat(document.getElementById

("payment_value").value)*0.03;

}
</script>