Woocommerce: Add Additional Fee on cart

custom.php

<?php

// Add additional fee ( Handling Fee etc. )
add_action( 'woocommerce_cart_calculate_fees','theme_prefix_additional_fees' );
function theme_prefix_additional_fees() {
     global $woocommerce;
 
     if ( is_admin() && ! defined( 'DOING_AJAX' ) )
          return;
 
     $fee = 5.00; // add amount

     $woocommerce->cart->add_fee( 'Handling', $fee, true, 'standard' );
}