How to Update records of a Sub-grid in CRM 2013 using OData JSON JQuery

Hello,

Below is my Product sub grid on Quote Entity.

Now On addition of new product , I am calculating Service tax and tax based on Price per unit, quantity and discount.

Now i need to set calculated service tax and tax value in sub grid.

I want to Update record of a Sub-grid in Quote Entity. I have tried below code, but still not able to update my sub grid .

function OnRefresh()
{ 
var gridControl = document.getElementById("quotedetailsGrid").control;
var  ids = gridControl.get_allRecordIds(); 	

for (i = 0; i < ids.length; i++) {

var quotedetail = new Object(); 
quotedetail.new_service_tax = "1000";					
var id = ids[i].replace("{", "").replace("}", "");										
QuoteProductRecord(id,quotedetail);

}
}


function QuoteProductRecord(id,quotedetail) {
 
var jsonEntity = window.JSON.stringify(quotedetail);

var ODataPath = Xrm.Page.context.getServerUrl() + "/XrmServices/2011/OrganizationData.svc/QuoteDetailSet";

$.ajax({
	type: "POST",
	contentType: "application/json; charset=utf-8",
	datatype: "json",
	data: jsonEntity,
	url: ODataPath + "(guid'" + id + "')",
	beforeSend: function (XMLHttpRequest) {
		XMLHttpRequest.setRequestHeader("Accept", "application/json");
		XMLHttpRequest.setRequestHeader("X-HTTP-Method", "MERGE");
	},
	success: function (data, textStatus, XmlHttpRequest) {

alert("Success");
			},
	error: function (XMLHttpRequest, textStatus, errorThrown) { }
});

}

Issue is that there is no error thrown, but still Service tax and tax value in sub grid is blank.

In JSON function, i have also tried to alert success message , but neither i got any success message nor any error message.