Fares are fixed from the airports.
To recap, from CDG to Paris you pay 50€ to the Right Bank, 55€ to the Left Bank. There is a 4€ charge for each passenger from 5 to 7. There is no charge for wheelchairs or luggage. Drivers are never tipped.
The fares are established by the Préfecture de Police which also licenses and oversees all taxis operations. Taximeters should indicate the fixed fare when departing the airport. If there is any discrepancy when arriving at your Paris destination, gather your luggage and pay the fixed fare, nothing more (noting the additional charges for more than 4 passengers). Take out your phone and take pictures of the taxi license plate and parking permit number found on the right front fender which should tame any recalcitrant driver. If you ever feel cheated by a taxi driver, note the required information and file a complaint with the Préfecture:
Taxi complaint form
If you forget the rates, they are written, in both English and French, on a sticker found on the left inside rear window of every taxi.