Like any web application framework, Sails can be used for e-commerce apps. Depending on your project's specific needs, you can use Sails as the base for your own custom solution, or integrate with an existing e-commerce platform.
When building a custom e-commerce solution on Sails, there are a number of possibilities for how to structure your data. A good place to start is with 4 models:
User (already included in the "Web app" template for new Sails apps),
Order. By including associations, you can track things like shopping carts and a user's individual order history.
If the prospect of rolling custom e-commerce features from scratch is rather daunting, you may consider building your Sails app on top of an existing Sails-based platform (e.g. Ymple).