Here is the solution,
$('.precio').keyup(function () {
var igvdolaresround = (Number($(this).val()) * 18) / 100;
console.log(Number(igvdolaresround));
var igvdolares = igvdolaresround /* not found (igvdolaresround).toFixed(2); */
var totaldolares = ((Number($(this).val()) + igvdolares).toFixed(2));
var igvsoles = ((igvdolares * 2.80).toFixed(2));
var totalsoles = ((totaldolares * 2.80).toFixed(2));
$('#igvdolares').val(Number(igvdolares).toFixed(2));
$('#totaldolares').val(totaldolares);
$('#igvsoles').val(igvsoles);
$('#totalsoles').val(totalsoles);
});
function maxLengthCheck(object) {
if (object.value.length > object.maxLength) object.value = object.value.slice(0, object.maxLength)
}
I have even made the change to your JSFiddle Code you can check that out. http://jsfiddle.net/XyqCw/1/