You are supposed to report ALL interest received. However, since TurboTax rounds all amounts to the nearest dollar (as permitted by the IRS and AFAIK all states, and required by many states), you should report nothing if total interest is 49 cents or less, or $1 if it's 50 cents to $1.49. If you need to report small amounts, enter it on a dummy 1099-INT in TurboTax (even though you didn't get a 1099-INT because you earned less than $10 in 2015).
