ICC Match Referee Javagal Srinath imposed the fines after Plessis' side was ruled to be two overs short of its target when time allowances were taken into consideration.
In accordance with the regulations of the ICC Code of Conduct for Players and Player Support Personnel governing minor over-rate offences, players are fined 10 per cent of their match fees for every over their side fails to bowl in the allotted time, with the captain fined double that amount.
The offence is contrary to Article 2.5.1 of the Code, which relates to minor over-rate offences.