Not sure about the ethos of your post but in any event, just so there'e no misunderstanding:
"Search engine traffic is one of the most important factors that decide the success of an online."
Not really, traffic is useful but just traffic. A website that concentrates on converting visitors to customers is what's needed, with search engine considerations second in the queue.
"A SEO friendly shopping cart doesn’t mean the features visible to you and your customers."
That kind of misses the whole point. Apart from conversion needs mentioned above, SEO is all about what is visible to customers. Apart from indirect value, such as good quality content drawing good quality links which help with search, modern search engines are primarily interested in content.
All the mentions of tags etc. have minor merit in some cases but major search engines don't even look at keyword tags, or several types of title tag, or most meta tags and only use description tags for snippets, not ranking.
The greatest technical enemy of shopping carts is poor configuration. Making crawling or understanding the site hard for search engines and visitors, or creating content duplication under different URLs. A far larger problem however is content, they are often no more than online brochures and even then filed with product descriptions that can be found on many other sites.
Build a unique and captivating site instead, make sure the web knows about this and keep building, keep enthralling. Search engines will soon be running up the road, desperate to include the popular and valuable to fulfil their business model. If you put up the same old same, you can spend your life filling tags all over the place, won't help.