[Plugin: WooCommerce – excelling eCommerce] XML Sitemaps. Issue with ?add-to-cart=

Hi there
Today I generated a sitemap using the xml generator site for my woocommerce store.
I noticed that there are lots of urls that look like this: <url>
<loc>http://www.mydomain.com/?add-to-cart=2114</loc&gt;
</url>
Obviously this is not very useful. How can I go about this?
Should I create the site manually and block the urls in the robots.txt?

M.

http://wordpress.org/extend/plugins/woocommerce/