To group multiple URLs under single Post, simply specify the same canonical link in all the relevant pages.
Parse.ly doesn't just track individual URLs, but actually groups links that refer to the same Post as one. This allows easier, simpler, and more accurate tracking of your content. Internally, we refer to this feature as "Link Aliases". Every Post has a "Canonical Link", but also has any number of aliases, which should be considered logically equivalent to the canonical link.
Here's an example of an article about the changing demographics of society that appeared on the web as a group of URLs:
The URL structure reveals itself that all of the URLs essentially are from the same article. First six URLs are the entire article, and then there are three alternative formats - printable, single page and mobile versions.
It's true that most traffic for this article typically ends up at the "Main Article URL", but tracking the post across all its incarnations is important, especially when you consider social media and search channels. For example, a search engine might get a hit on page 3 of the article for certain keywords. Your Twitter audience might choose to tweet the single-page version of the article, or the mobile version, rather than the "main" article URL.