When you are a government servant, accepting money through any means and forms other than your salary is WRONG. Be 10 sen or 10 billion. It's still WRONG. It's as simple as that.
Even if your culture sees it as normal, the culture of the government sees it as WRONG. And since you are a government servant, you are tied to the government culture. And therefore, it is undoubtedly, unequivocally, undeniably WRONG.
WRONG! WRONG! WRONG!