$(function() {
  $("#subtotal").html(sumColumn(4));
  $("#total").html(sumColumn(5));
});

function sumColumn(index) {
  var total = 0;
  $("td:nth-child(" + index + ")").each(function() {
    total += parseInt($(this).text(), 10) || 0;
  });  
  return total;
}


  

    
ClientName
    
ItemName
    
Quantity
    
12
    
34
  
  

    
ClientName
    
ItemName
    
Quantity
    
56
    
78
  
  

    
ClientName
    
ItemName
    
Quantity
    
90
    
12
  
  

    
Totals