[WooCommerce] Add surcharge to your cart / checkout

functions.php

add_action( 'woocommerce_cart_calculate_fees','woocommerce_surcharge' );
function woocommerce_surcharge() {
  global $woocommerce;
        if ( is_admin() && ! defined( 'DOING_AJAX' ) )
                return;
        $percentage = 0.01;
        $surcharge = ( $woocommerce->cart->cart_contents_total + $woocommerce->cart->shipping_total ) * $percentage;    
        $woocommerce->cart->add_fee( 'Surcharge', $surcharge, true, '' );

}