Hi,
Yes. That setting is for the products listing pages of your menu item.
For the product detail page, it bases itself on the main setting in the HikaShop configuration.
There is no mechanism to display the price with or without taxes base on the user group.
So you would have to edit the file product / listing_price.php via the menu Display>Views and add such code at the beginning:
<?php
$my = JFactory::getUser();
jimport('joomla.access.access');
$userGroups = JAccess::getGroupsByUser($my->id);
if(in_array(XXX, $userGroups))
$this->params->set('price_with_tax', 0);
?>
where XXX is the id of the user group for your business clients and that will force the display of the prices without taxes for them, on both the listings and the product details pages.