You can increase the number of Twitter followers on Twitter easily by optimizing your profile to certain keywords.
Twitter lets users do keywords searches to find people to follow and those to reply to.
If you want your e-commerce website to be discovered on Twitter when somebody is searching for a specific keyword, you can add it in your Twitter profile.
This way, every when someone searches for the selected keyword, the website whose icon is displayed on results of the search will be displayed as a reference on the Twitter stream.
When a tweet that contains your link is sent out the hash tag will be replaced by your keyword as element of the tweet.
Your links should be clickable, so that active users can click on them and be taken directly to your website.