gistfile1.php

<?php
/**
 * WooCommerce Extra Feature
 * --------------------------
 *
 * Add custom fee to cart automatically
 *
 */
function woo_add_cart_fee() {

  global $woocommerce;
	
	if ( is_cart() ) {
		$woocommerce->cart->add_fee( __('Custom', 'woocommerce'), 5 );
	}
	
}
add_action( 'woocommerce_before_cart_table', 'woo_add_cart_fee' );