It's just a powerful symbol. I've been trying to collect different Chinese province coins and trust me, it's a lot harder than you think. http://www.gxseries.com/numis/china/china_province.htm Ok, not necessary harder but it's not cheap.
Also, a symbol of stature in a ranking system. The emperor would be adorned with a dragon on clothing or ornaments and his dragons would all have four claws, and if anyone else was caught wearing a dragon with four claws they would be killed on sight if my memory serves me right. Commoners would wear 5 or 6 clawed dragons to show their status in the society. So, it was natural to have coinage bear a dragon to represent the power and strength of the currency, during certain dynastys.
For a basic understanding of the meaning of the dragon on Chinese coins please see The Hidden or Implied Meaning of Chinese Charm Symbols. Gary
Actually, the "five claw" dragon symbol could only be used by emperors. "Four claw" and "three claw" dragon symbols could be used by those of lesser stature. As an illustration, please see this Chinese banknote with a vignette of Chinese Emperor Qianlong with "five claw" dragons on the right and left borders. Gary
