addfee.php

<?php

// This variable value is passed to our function
$bookable_total = 1;

function woo_add_cart_fee( $bookable_total = 0 ) {
    //global $bookable_total;

    /*if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;*/

    // just for this example
    //$item_count = 0;
    //$item_fee = 5;

    // going through each cart items
    //foreach( WC()->cart->get_cart() as $values ) {
        //$item = $values['data'];
        //if ( empty( $item ) )
        //    break;
        // getting the cart item_id
        //$item_id = $item->id;
        //$item_count++;
        // your calculations
    //}

    // We test $bookable_total value, defined to '1' outside our function
    // and to 'O' if not defined outside (in this case the fee will be '0')
    //$fee = $item_count * $bookable_total * $item_fee;
    $fee = 120000;

    // add_fee method (TAX will NOT be applied here)
    WC()->cart->add_fee( 'Impuesto por viajes: ', $fee, false );

}
add_action( 'woocommerce_cart_calculate_fees','woo_add_cart_fee' );

?>