Can anyone help me in calculations?

Try this as custom calculation script of "TOTALTOTAL" field:

var total = 0;
var tax = Number(this.getField("TOTALTAX").valueAsString);
var ship = Number(this.getField("TOTALSHIPPING").valueAsString);

for(var i=1; i<=7; i++){
var qty = Number(this.getField("QTY"+i).valueAsString);
var price = Number(this.getField("PRICE"+i).valueAsString);
var dsc = Number(this.getField("DISCOUNT"+i).valueAsString);
if (qty !== 0 && price !== 0) {
var itemTotal = qty * price * (1 - dsc);
this.getField("TOTAL" + i).value = itemTotal;
total += itemTotal;} 
else {
this.getField("TOTAL" + i).value = "";}}
event.value = (total*(1+tax))+ship;