How to calculate order total after check out

I have calculated a different custom order total in Woocommerce:

add_action( 'woocommerce_checkout_create_order', 'change_total_on_checking', 20, 1 );
function change_total_on_checking( $order ) {
    // Get order total
    $total = $order->get_total();

    $orderproduct = $order->get_items();
    $tax_rate     = WC_Tax::get_rates( $orderproduct );

    if ($tax_rate == "10") {
        $percent10 = $total * $tax_rate; 
    }

    if ( $tax_rate == "4" ){
        $percent4 = $total * $tax_rate;
    }

    ## -- fai check e calcoli -- ##
    $new_total = $total + $percent4 + $percent10; // <== Fake calculation

    // imposta un calcolo nuovo
    $order->set_total( $new_total );
}

But my calculations don’t work and I’m not able to make it for instance.

Any advice or help please?

Answer

Is there ever a time you would have both tax rates? Otherwise, I would think one variable for taxes would be enough, like so:

if ($tax_rate == "10") {
    $tax_total = $total * $tax_rate; 
}

if ( $tax_rate == "4" ){
    $tax_total = $total * $tax_rate;
}

## -- fai check e calcoli -- ##
$new_total = $total + $tax_total

Also, what do you mean your calculations are working?