This point was well illustrated in Back to the Future II, in the scene where, or should I say when, Marty and Doc are in the 50's, and Doc opens up an attache case containing various denominations spanning different time periods, so as to prevent an intertemporal incident in which the errant time traveler attempts to pay a present debt with future fiat money.
In contrast, Alex, the protagonist of Robert Heinlien's Job: A Comedy of Justice is wont to carry his lifes' savings on his person at all times in the form of gold coins. The reason for this odd behavior is in response to an especially cruel Supreme Being, who like a cat toying with a mouse, is continuously whisking Alex from one parallel universe to the next as soon as Alex is getting in the swing of things. (Apparently this malicious God is capable of remapping objects in the multiverse, but won't strip Alex of his vestments in the process.)
If there ever was a cause that fellow time-travelers and world-walkers could unite behind, this is it.