Let there be $x$ pennies. Therefore, there are $2x$ dimes and $3(2x)=6x$ quarters. Since pennies are 0.01$, dimes are 0.10$, and quarters are$$0.25$, the total amount of money is $$0.01x+(2)(0.10x)+(6)(0.25x)=$$$1.71x$. Therefore, any amount of money must be a multiple of 1.71$. Since the answer choices are all whole dollar amounts, we multiply by $100$ to get a whole dollar number: 171$. Notice that twice this is$$342$, which is answer choice $\boxed{\text{C}}$.