There is always confusion about various PST/HST rates. There are various PST/HST rates that are for the provinces - but how it is determined if they are calculated and added or not.  

D Memo D17-1-22 Covers the requirement

https://www.cbsa-asfc.gc.ca/publications/dm-md/d17/d17-1-22-eng.html

Below is the description:

 
For casual goods, CBSA will only collect the HST (when goods are destined to a participating province), or PST if the goods enter a PST province, destined for the same PST province.  

 
Example: 
If the goods were to enter into Manitoba (PST collection agreement) but are destined for Saskatchewan (PST collection agreement), then only the GST is collected.
 

Below/attached are the supporting documents from CSCB and CBSA: