I bought 3 x $20 CAD cards at £10.94 each to give me $60CAD total.
When setting up your Nintendo account for the Canada region select ‘Alberta’ as your province, this is the province with the lowest tax rate (5%).
Then I purchased Lego Worlds, Lego City Undercover, Rocket League, Violett and The Sparkle 2. I used my nintendo reward points gained from the earlier purchases of Lego games to make up the difference in price on the later games.
In the end I had $0.91 CAD and 89 reward points remaining. I messed up a little and didn’t buy them in the order listed above, if I had done then I possibly could have bought something different to Violett & Sparkle and used up my remaining credit more completely but I am pretty happy with 5 new games for approx £30.