How to add coins from different currencies

Question

We are teaching a class where we need to teach about currency. We would like our students to add and demonstrate using different currencies across the world.

(e.g. Country=US, How much does 3 nickels + 2 pennies + 3 dimes)
(e.g. Country=UK, ...)
(e.g. Country=JAPAN, ...)
(e.g. Country=CHINA, ....)
(e.g. Country=AUSTRALIA, ...)

Is there any sample code, which demonstrates conversion of coins in different currencies?

Note: If it also contains the conversion between smaller units (e.g. b/w nickels, pennies, dimes, dollar) it would be useful.