Transaction fees are charged per parking transaction and per parking extension, based on where you park. Not all parking providers charge a transaction fee in addition to posted parking rates; some parking providers waive the transaction fee.
To learn more about transaction fees in your area, view the Help Center article for your city/area in the Parking Area Specific Info forum by typing in your city name as a keyword and clicking 'search'.
Also, in certain locations the parking operator absorbs the cost of the parking transaction fee on your behalf. Visit this article to see which locations waive the transaction fee.