Which means that bringing a pocket full of Canadian change into the US is in fact a breach of the Helms BurtonAct: not something that anyone ever bothers about of course.
The embargo was tightened in 1963 after the Cuban Missile Crisis and was reinforced in October 1992 by the Cuban Democracy Act and in 1996 by the Cuban Liberty and Democracy Solidarity Act (known as the Helms-Burton Act).