Sorry, please ignore my previous reply as I misunderstood your question.
Please use render callback in a column to hide total value in aggregate cell when corresponding group title row is expanded.
{title: "Gold", dataIndx: "gold", width: 100, dataType:'integer',
tpCls: 'gold',denyGroup: true, denyPivot: true,
render: function(ui){
var rd = ui.rowData;
if( !rd.pq_close ){
return {text: ""};
}
}
},