Hi,
Caching is a vast subject.
If you cache whole pages, when you add something to the cart, the cache has to be cleared, otherwise, you won't see the changes on the page.
HikaShop (and other ecommerce solutions for Joomla work in the same way when they support caching), is rendered compatible with the page caching of Joomla by clearing the cache each time something changes on the page.
If your website is a shop, everyone has something different in their cart and thus the pages will be different for everyone. In that case, there is actually no reason to have caching on your website since the cache is common to everyone and will be erased all the time. It's even more efficient to keep it turned off.
Also, if you have other kind of caching, modules, JS, CSS, third party extensions, HikaShop might not support them based on how they are done and configured. So you might get issues during the checkout or other parts of the website.
What I can say is that we have other merchants using HikaShop and the joomla cache at the same time on their website and it works fine for them. But we also had other merchants with caching or user session (that's a different subject, but the resulting problems can sometimes look similar) issues, which is why we recommend to change these options and and see if that helps.