Using "the" actually relies a lot on context. It means both you and I know which thing is meant.
In this case, by using "the", "which" pennies and pounds is already implied: the phrase means the pennies which you have. Sometimes "the" suggests the most obvious possibility, such as "the park / the cafe" or that the thing logically exists: "Upstairs I found a bedroom. THE bed was under THE window." (We can logically assume that a bedroom has a bed, and probably a window, so we use "the".)
Without "the", the phrase sounds weak and random.