jc

https://docs.woocommerce.com/document/add-a-surcharge-to-cart-and-checkout-uses-fees-api/
here

add_action( ‘woocommerce_cart_calculate_fees’,’woocommerce_custom_surcharge’ );
unction woocommerce_custom_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, ” );

}