@Jippie
:Usually when the "total price" ends with .00EUR/GBP it's with taxes.
Just checked your theory. I'm in IRL. Checked DUB>MAD return, and DUB>Malaga return dates 20 to 29th Sep 2011. In both cases all prices listed in the 7 boxes under "previous week" and "next week" end in .99 EUR. However all the flight to Malaga have Taxes and all the flights to Madrid don't.
Did I understand you correctly?