Yes you can. I have bought reloading tools from Brownells, ebay, Amazon, and directly from CH4D. All were mailed via US Postal Service and none incurred any special fees at the border.
Brownells, ebay, and Amazon have filter options that will show you items that can be shipped to Canada. Some sellers just won't deal with Canada out of their own preferences. Some firearms related items are regulated by US law and either cannot be exported or require the exporter to have a license to do so, although I don't think that applies too much to reloading tools.
If you are looking for any Lee tools, my first choice after my local gun shop is Higginson Powders outside of Ottawa or wherevever they are. They are good to deal with.
I've only ordered from US sources when more local sources are out of stock, for vintage collectable tools like out of production Lee Loaders, or for dies for oddball calibres.