Can a presidential pardon erase a fine?

Yes, if they were part of a federal criminal sentence.

https://clemency.com/presidential-pardon-rules

Probably, though being pardoned by Trump is an indelible mark of bad character that is worse than any fine.

ONLY IF it was a Federal fine!!!

The catch is that by accepting a Presidential Pardon, you are admitting your guilt & thereby giving up your 5th Amendment Right to protect yourself from self incrimination. So, when you have a Federal charge, you can NO longer plead the 5th on certain topics. Now, state charges are a totally different ballgame.