Tax is whatever the sales tax is in your province. This varies from 5% to 15%.
This is one case where it is likely that the new and much despised Global Shipping Program would be useful to you. One of the advantages of the program is that it tells the buyer what border fees will be charged, adds them to the selling and shipping prices, and gives you the total.
You have to pay that total, including the applicable fees, duty and shipping, before the seller will send the package.
There is some thought that this new program may be a little cheaper on high-value goods than shipping by post or courier, because the trans-shipper (Pitney Bowes) charges lower fees than others.
Canada Post will not insure high value jewellry against loss or damage in shipping. Couriers will.
Courier shipping (like UPS) may appear cheaper, but they charge a substantial customs brokerage fee ($25 or up) on your doorstep without prior notice and will not release the package until you pay.
Frankly, as a new buyer, this is a risky purchase. This is not a reflection on your seller, but mail order , especially cross-border is always fraught.
