As far as I know yes, there is a $100 mininmum.
Discussion
Buying minimum or withdrawal minimum?
Buying minimum is $10, withdrawal minimum is $100.
Proper terminology at Canada Post is a Loadhub Payment but don't be surprised if they don't know what it is.....just get them to shoot their gun on your QR and tell them how much you want to pay.
I did a $20 CAD test buy.