HikaShop does not have any control on Joomla's cache. If Joomla caches a page, HikaShop won't be able to tell it to clear the cache because something changed. That's why we recommend to turn that off in Joomla.
Now that doesn't mean that HikaShop doesn't already have some caching in place. For example, the cart object is loaded only once per page even if requested several times for different places in order to speed up the process.
On HikaShop's end, it would be totally possible to add, on top of the optimizations we already have, a cache plugin to store some areas which don't change, but since almost anything in HikaShop can be dynamic, that's not so useful/easy to do.
Also, you can use some other forms of cache to speed up the processing like APC.