Teena I do exactly what you are doing. 87% of my sales are to the US and together with custom work, the total $ going through make it worth the HASSLE of dealing in two currencies. I list on Etsy and my own website in US$. I opened a bank account across the border in the US - totally legal - hooked my PayPal US$ account to it, opened a US$ bank account locally, and have my normal CA$ Bank account and PayPal CA$ account. So that makes 5 bank accounts basically!
The advantage? NO currency exchange fees by everyone who does a transfer! When you start adding up 2% here and 2.5% there, it's ridiculous! So the flow looks like this:
Customer pays in US$ to Paypal
Once enough $ accumulate about every two months, I transfer to the bank located in the US
Then when needed I write a cheque on that US account with my other US account located close to home.
I use the company Vancouver Currency and Bullion Exchange and once every couple months I email for an exchange rate for them to buy US funds and once accepted, they automatically debit my US bank and deposit to my CA bank.
The DIFFERENCE is exchange Gain/Loss and that is recorded on the books.
I know it sounds complex, but once set up, it's only a few minutes' work every two months and saves me MUCH exchange over the year.
Only exception is ETSY - They payout Direct Checkout US$ into CA$ doing the exchange and it's difficult to account for since it's outside my system and needs separate accounting :/
Basically harder for the seller but easier for the buyer, which is always for the best!
Diane