I do not know the actual halacha (and I could possibly be totally off-base), but this is my response. Before you ask your LOR, ask yourself: I broke the law by speeding or parking illegally. Can I honestly use tzedaka money to pay a fine for a crime I committed? Can we EVER use tzedaka to pay a fine for a crime of any type, of which we are guilty? If NOT guilty, then I can see a place for asking the shailah of a rov, because in that case, you could argue the point that you are being forced to give a donation to the government, which uses those funds for a variety of reasons,among them possibly charitable ones. if however, you are guilty, you are paying a k’nas, which is not a donation voluntary or otherwise, but a punishment. Therefore, IMO, that should come out of your own pocket in addition to money you set aside for tzedaka, not in lieu of it.