Hi,
That's a good point. I looked at the history of the changes around this and as far as I can go back, it has always been like that for no particular reason.
I think this could be changed by changing the line:
$cart->package['zone'] = $zone_id;
to:
$cart->package['zone'] = $tax_zone_id;
and the line:
$currencyClass->processShippings($cart->usable_methods->shipping, $cart, $zone_id);
to:
$currencyClass->processShippings($cart->usable_methods->shipping, $cart, $tax_zone_id);
in the file administrator/components/com_hikashop/classes/cart.php
Can you confirm that this solves the problem for you ?