Depending on the Prefix
If you go to your local library you can find a Charlton Guide to Canadian paper money and it will inform you which prefixes hold premiums. I recommend you do this if you're interested in collecting. A new catalogue is soon to be released (mid July) so hang on to get a copy, or buy the old edition at a discount (however the info will be somewhat dated).
Some of the FDT to FDZ (Knight/Thiessen) regular issue already appear to be gaining steam since this is the rarest signature of this short-lived series. The 2002 Knight-Dodge prefixes are all fairly common except for those which have a slight missing circle anomaly on the left margin. There were very few of the missing prefixes (2003 BEL, 03 BER, 03BEK and 03 BEP) so they're keepers. 2004 (Jenkin/Dodge) BER and BET are also worth keeping.
The $5 have less of an idiosyncratic history, and are less noteworthy. The chances of catching an (eg AOB) insert are low. There are some noteworthy change-overs like the 2001 AOF or 2004 HOH... but not much other than that. As I said, borrow a guide from the library, and it will inform you best what to keep an eye on.
If they're a common prefix then you're better off trading them here (upgrading to something rare) or selling them as a sequential lot on ebay. There are plenty of common prefixes kicking about but some collectors are still interested in getting their hands on a few.
