You will not have to pay sales tax. The Chanel shop in Nordys is not part of the same entity as the freestanding Chanel boutiques. I order my Chanel bags from Las Vegas and pay no sales tax.
The Portland Nordy is opening a Chanel shop. If I go to Portland and buy a bag and take it with me I pay no sales tax because Oregon has no sales tax. However, if you ship the bag to Seattle, then you must pay sales tax.
Portland Saks has Chanel as well. For little items I sometimes buy from Nordstrom but for big purchases I never do.