Limiting woocommerce line_total decimal length

Just round the decimal to two digit as per your requirement.

$myID = 2859;
$myorder = new WC_Order($myID);

    foreach ($myorder->get_items('line_item') as $item) {
         $rounded_total = round($item["line_total"],2);// allow 2 decimal and avoid further
        $Data = $Data.OrderLine($item["name"], $rounded_total, $item["line_tax"], $item["qty"], "piece", "x");
    }