It's somewhat counter-intuitive but to really drive sales in Canada you have to think differently than the stores in the US. In the US market price seems to be king, shipping is dirt cheap & very very fast (state to state in under a week!!! - here it takes 3 days just to get from the suburbs to the city's central sorting station) & there's an army of stores all fighting for your pennies over there... (while vender selection is so much more limited here)
In the Canadian market you're not likely gonna be able to compete head to head on price to make any worth while profit, most US buyers will buy US first anyway. What you need to do is have allot of stock, you'll need a wide variety of stock & you need to keep the stock fresh/recent. Postage is expensive here so you must make it worth the buyer's time & snag as many things in their wanted lists as you possibly can all at one time - "Lot & Lots of lots" will grab the sales better then the best or even good prices - Canadians know shipping costs will well out way saving 3 cents on a brick, it's gonna cost & take 3 or 4 weeks to arrive at their door so best have as near to everything in one parcel as you can.
Also since there are so fewer Canadian based stores Canadians will choose their favourites & generally stick with them over & over again, you MUST make their buying experience fun & noteworthy to get on their go-to list (it's not always easy to break into at first). This means no mistakes (an accurate order is an imperative), nothing messed up in quality (if it's scratched say so - under promise & over deliver), freebies are remembered (toss in a $3 keychain on a big order is inexpensive for you but makes a surprising impact, as does a little bag of extra related parts - get remembered!), package well (your parcel's presentation is always your personal introduction, show the buyer you respect their choice in you & send things neat & safely packaged - do not use used dipper boxes or food/personal chaff, everyone wants to feel like the item in their hand is fresh & new, even if it's used parts)
Pay attention & learn from your buyers, watch out for trends in their buying's this will guide you toward what inventory you will want to carry & eventually you'll find specializations that you can leverage... for example in my zone the sales of railroad related parts is overwhelming, everything sells as fast as I can bring it in - similarly for ninjago & technics, while classic space & castle is obviously in much less demand. but don't be afraid to experiment some with the panned lines - if no one carries Bionicle parts maybe they will do well for you if you're the only game in town.
Have fun with it - it shows if you enjoy what you're offering.
one last thing... don't bother with 5 or 10% off sales - they are really quite meaningless & have no real affect on prices to the buyer nor to your profit margin, it's really kinda insulting to the buyers too, it's just like saying "this is all I think your shopping is worth to me"... it's better to have no sale & have confident in your set prices that offering anything less than 25% off.
A starting tip is to boost your feedback up to about 100+ as fast as you can (anything after 3 digits doesn't matter for visual presentation or respect) find the stores that never fail to leave feedback & buy a bunch of little letter mail-able items to get your numbers up, doesn't matter what the parts are - just drop them into your store & recoupe some of your investment - you're not buying the parts you're buying the feedback.