What do you mean by when you got to the destination it was 4.80, and when you stopped it was 6.20? How much travelling/time was there between destination and stopping? (they'll charge you for time taken if the speed is low enough, ie for idling at traffic lights)
There could be some levy added at the end as a percentage for the rising cost of petrol or something. Or if you called the taxi to come pick you up (although where I live they add that surchage at the beginning of the trip)
If it's bothering you, next time ask why. There's probably a legit reason for it. If there's not, be thankful it was only $1.40 