$consulta = "SELECT unidad_de_medida, itemcode as 'codigo' , qty as 'cantidad', itemname as 'descripcion',  retailsprice as 'valor_unitario', (retailsprice + IGV) as 'precio_unitario', discount as descuento ,    total as 'subtotal', igv ,  ROUND((total + igv) ,2) as 'total', taxapply as 'tipo_de_igv'   FROM sales_item where sales_id='$salesid'";

$query = mysqli_query($enlace, $consulta);

    for ($set = array (); $row = $query->fetch_assoc(); $set[] = $row);