2%: Market Square, Lancre Town (crowns) 
    3%: Market Square, Ohulan-Cutash (crowns) 
    7%: Market Square, Escrow (crowns) 
    10%: Widdershins Broadway, Ankh-Morpork (dollars)

The coop is very useful for anyone who spends time in the ramtops.
With low deposit charges at most branches and a good reputation, despite somewhat paranoid staff, the coop is an excellent place to store spare funds.