Ok, good point about the people off 100 years ago not being able to recognise our contemporary currency, but the timeframe doesn't have to be so big.
Go back in your time machine to 1991 with $1,000 in your pocket, put it in the bank at 5%, travel back too 2011, it's worth $2,653. Take your $2,653 back and turn it into $7,039. Do it over and over, and you're a very rich time traveller. Instant compound interest, but without the waiting!
Has the bank reported the $10,000+ cash deposit, as they are required to by law? The IRS would like you to file an 8300, and the DEA would like to know your occupation.