The reason that the interest rate can be express to more than two DPs is because often the disclosure is part of the deposit contract, and you need the accurate interest rate in the contract.
So your disclosure can say 0.049% for the interest rate and 0.05% for the APY. It's the ad that can't reflect the actual interest rate to three DPs. I guess I don't see what the problem is. In normal times when rates are in the 3% range, disclosed interest rates are almost always lower than the disclosed APYs.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8