Hi,
Indeed, the answers here don't apply anymore.
Nowadays, HikaShop comes with tools so that you don't have to modify anything.
In your orders listing, you have a columns button on the top right corner:
i.imgur.com/SlPryez.png
There, below the "Total" column, you have one column per tax rate which you previous configured in the System>Taxes' "Manage rates" button. If you check these tax rate columns, the orders listing will directly display the tax amount for each tax rate, without the need for any customization.
So it's actually similar to the solution talked about above, but even better as the taxes are broken down per tax rate (if you have different tax rates for different products in your shop, it's really useful).
Also, since then, if you click on the "export" button to get a CSV export of the orders data, you'll find an "order_full_taxes" column which will contain the total tax amount for each order.
Finally, we've also revamped the tax rates listing interface. If you go in the System>Taxes menu and click on the "manage rates" button, you'll see a listing of your tax rates. And for each tax rate, you can see the total amount of purchased goods without taxes, the total taxed amount, and the total amount of taxes. And you can use the dates and order statuses filters to restrict this calculations.
This way, you can get the total amounts calculated for you, without having to export the order data and do the calculations yourself.