No single person invented tar. Natural tar-like materials were found in the ground, and human-made tar was probably discovered independently by different cultures that heated wood, bark, or other organic material.
Tar does not have one inventor in the modern sense. It is a family of materials discovered through observation and repeated craft practice. People could find natural bitumen at seeps and deposits, and they could also notice that heating certain woods, barks, or resins produced sticky dark substances with useful properties.
The knowledge needed to make tar is practical rather than abstract. A person has to understand that fire can transform a material without simply burning it away. That is not a trivial discovery. Making birch tar, for example, requires controlled heating and some way of collecting the product. It is not just a campfire accident.
Different kinds of tar probably have different discovery histories. Birch-bark tar belongs to prehistoric toolmaking. Pine tar belongs to forest craft, timber, rope, and maritime life. Coal tar belongs to industrial processing of coal. Road and roofing materials grew from later industrial use of bituminous substances.
The better way to ask the question is not who invented tar, but who learned to use which tar. Ancient toolmakers, shipbuilders, charcoal burners, tar burners, roofers, chemists, and road builders all belong to the story.