Not all of the statutes for Pennsylvania are on line and that one--I am only finding bits and pieces to it. I think it is a misdemeanor.
To be sure you should go to the courthouse where you paid the fine and find out what is on your record.
Application for the USPS asks here:
7a. Have you ever been convicted of a crime or are you now under charges for any offense against the Law?
You may omit: (1) any charges that were dismissed or resulted in acquittal; (2) any conviction that has been set aside, vacated, annulled, expunged, or sealed; (3) any offense that was finally adjudicated in a juvenile court or juvenile delinquency proceeding; and (4) any charges that resulted only in a conviction of a noncriminal offense. All felony and misdemeanor convictions and all convictions in state and federal courts are criminal convictions and must be disclosed. Disclosure of such convictions is required even if you did not spend any time in jail and/or were not required to pay a fine.
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If what you find out needs to be sealed or expunged, then go here:
http://www.uslegalforms.com/lawdigest/expungement-criminal-records-law.php/PA/PA-EXP.htm