Q. I was attending a levaya and before they covered the aron with earth, someone approached the kever and threw some coins into the kever. The Rabbi, maybe did not notice, and did nothing. Is that not a goyshe minhag?
Should we have made an issue and have the coins taken out ?
 
A. Placing coins on the mouth or the eyes of the deceased would normally be understood as a pagan tradition known as Charon’s obol. Greek and Latin sources label the coin as an obol and explain that it is as a payment or bribe to Charon, the ferryman who conveys souls across the river that divides the world of the living from the world of the dead. (Wikipedia)
However we do find something similar in Maavar Yabok (Sifsei Tzedek 7: p. 57) that those who make hakofos around the kever before the burial, would place pieces of coins, silver and copper, representing the three parts of the neshama of the deceased, and then give them to the poor.
Gesher Hachaim (1: p. 135) quotes a similar minhag of placing seven coins or pieces of them on the abdomen of the deceased and then throwing them aside and away from the body, while reciting the posuk (Bereshis 25: 6) “Ulivnei Hapilagshim Ash er Leavrohom. (And to the sons of Abraham’s concubines, Abraham gave gifts, and he sent them away from his son.)” Shulchan Gavoha (Y.D. 3: 368: 5) quotes the tradition of the Saloniki Kehila, to throw four copper coins to the four cardinal points and away from the departed, as if giving to the spirits that may have been created by him their inheritance. This is done to avoid those spirits following the deceased to the Olam Habah to collect their share.
Minhagei Yisroel (p. 62, 63) also quotes different Sephardic traditions in regards to coins.
Horav Shlomo Miller’s Shlit’a opinion is that people should follow the established traditions of their ancestors and their communities. It would be improper for an attending individual to pursue his own minhag on others, that may not maintain that tradition. However, if it did happen, then embarrassing someone publicly or creating a turmoil and uproar at a levaya should in principle be avoided.
 
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a