Hi,
I am not an expert, so please do not take my answer very seriously. What you mention, of making a canonical tag pointing to the same URL, looks fine. In my understanding, canonical tags were created to tell the search engines that a page is the right one, even if the system you are using creates address that could look like duplicate content. For example, if you are using a Content Management System like wordpress or Joomla, you could have the following:
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http://domain.com/date/month/page1 and so on.
Search engines (again, I am not sure, I am just a newbee), could think all this pages are duplicate content, and could penalize you for this. But if you indicate with the canonical tag that the right url is http://domain.com/page1, then you are safe.
I hope somebody with more experience could help you better,
Best Regards,
Daniel
