Hi,
There is no option for that by default in HikaShop.
However, you can customize the files of the view product of the front end via the menu Display->Views to achieve such thing provided that you know PHP and HTML.
You would have to add an input box for each product with the name data[PRODUCT_ID] (you of course need to replace the product id in that name) and then a add to cart input button at the bottom with a global form around the listing directing to the page index.php?option=com_hikashop&ctrl=product&task=updatecart that will submit everything to the cart.
You will need to get the latest version of hikashop (1.4.2) as with previous versions, if the user clicks a second time on an add to cart button, the first products would be removed from the cart.