POSSESSION <GRAM NOT ARRESTED ALL MONEY SIEZED

First offense no prior criminal record, pulled over (no reason given) on my way to the beach to party with less than a gram total on me, police did not run drivers liscenses or arrest me. He charged me with simple possession fined me $565 and took all of the money that i had on me ($830) because he said he had to seize all of my money or take me to jail! i go to court tomorrow and im confused about what is going to happen to me as well as why the police officers took my money (which was all of the money i had to my name). what should i do or what do you think will happen to me???