As with any State that is in the northern part of the United States, Wisconsin is home to many businesses which do business with Canada on a regular basis. As such, there are many messenger WI based companies that are very familiar with all of the regulations that apply to international shipping. They can give you a better idea about the exact amount that you can expect to pay on any given shipment, but the basic rule is that yes, there are extra fees and taxes which are going to apply.
Many of us forget that shipping to Canada is really no different than shipping overseas. This is true to the extent that shipping to Canada is still shipping across an international border, and as such, there are many more rules and regulations that apply, which always means more expensive shipping costs.
The first thing that you'll have to worry about when shipping to Canada is that you'll have to pay the tax on any goods that you are shipping. Canada has different taxes, depending on which province you're shipping to; which is something that your courier should be able to give more information on. Some provinces only have a GST (general sales tax) some have a GST and PST (provincial sales tax) and some have now switched to a HST (harmonized sales tax) which is the GST and PST combined to a single tax.
When shipping internationally you will also have to pay a customs broker fee in order to get your shipment across the border. There is a good money saving tip though for anyone that needs a brokers services. They charge by the shipment, so if you can combine a few shipments into one while going across the border and have them distributed in Canada, you can save yourself a little money.
Those are the basic fees that you're going to have to pay, but keep in mind that there could be hidden costs based on what exactly it is that you're shipping. Certain kinds of goods require additional licenses or permits to ship across international borders. The only way to tell if those are going to apply to anything that you're trying to ship is to speak directly with your courier company and describe in detail what is going to be contained in your packages. They should then be able to give you an accurate cost assessment.