You might check the quality of those old bills (are they in good condition?) there is a market for them, value depending on condition, denomination, year printed, where it was printed etc. There is probably more value in that paper than you can get asking Uncle Sam to give you $5 worth of gold for a $5 old bank note.
Condition is almost everything when you're talking about paper currency. Sometimes, just a single crease will destroy the numismatic value. Year of printing, and most importantly, the series letter is also important. The series is critical, because they don't actually change the year printed each year like they do on coinage. IIRC, the 1953 series ran for about 4 or 5 years. A 1953A might be more valuable than a 1953b.
There is also weird stuff that can make an otherwise uninteresting bill more valuable, like the serial number. Some folks try to collect bills with repeating digits. A silver certificate with 8-2s in the serial number might bring considerably more than the same bill with some random string, or if you were lucky enough to have a SN with 12345678.
In general though, folks who really collect paper money look at condition, and series.
There are some really beautiful engravings on some 19th century currency. If I were into paper, I that's the kind of thing I'd be most interested in.