Spree Commerce, which is an open-source e-commerce solution used by the biggest retail brands as well as single-product small-businesses, has some nice Search Engine Optimization (SEO) features:
- Relevant, Meaningful URLs
- On Page Keyword Targeting
- Clean Content thanks to Twitter Bootstrap, a responsive CSS framework search-enginge-friendly
- On Site Performance Optimization Minimizing HTTP requests for better search engine crawler behavior
- Google Analytics integration
However please note that there are other factors not related to your e-commerce solution which might affect your Google rankings:
- external links and their quality
- server performance and capabilities
These areas should not be ignored.