No, Shipping Assistant is not compatible with Mac. It was released only for Windows version, but there is an alternative called SendIt that was developed for Mac OS X. To check for additional information access the website: https://www.brinscall.com/sendIT/Home.html
Additionally, download Wine Bottler on Mac and then you can run Shipping Assistant as a Windows application. Wine Bottler makes it easy to run Windows applications on OS X.