No, I might have trouble with that one.

The first problem there is that it depends whether the "value" referred to is "face value" or "what you can sell them for"; a modern dime and an 1878 silver 20 cent piece have the right face value, but you could sell them for rather a lot more; and maybe two old century coins with a total face value of a lot less than 30 cents could be sold for 30 cents. So I don't know whether the answer is " an old 20 cent coin and a dime" or "you can't do that" or "an old 3 cent piece and an old half dime" (I suspect that the last is worth a lot more than 30 cents, but it illustrates the point). Or maybe it's something else altogether - I don't really know about American coinage, and of course Canadian coinage is different again (for example they had 20 cent coins about 20 years befor the USA did and dropped them 6 years before the US had them) and I haven't a clue which countries of Central or South America (or the Caribbean) ever had coins denominated in cents.

My best guess would be that the "right" answer to the riddle is "forgeries", but there's a good chance that I would be completely wrong.

So I definitely have trouble with that riddle.