I just checked the XE site and today's rate for US is J 90.74 - CDN is J 91.0267. Now we all know that these are not the rates we get but they are close. For the inconvenience of a double exchange I don't find it worth it. That being said, I do use US for my taxi to Negril since the driver prefers them.
Here's a link for you:
http://www.xe.com/ucc/convert/?Amount=1&From=CAD&To=JMD






