This new feature came about because occassionally I have had people ask how do you handle both commercial and residential property in the same database.
In some countries such as New Zealand and Australia residential property transactions are exempty from GST, however commercial properties still incur GST on income and expense transactions. Previously this was hard to handle. But now you can mark a property as transaction tax exempt. This means when you enter income or expense transactions for these properties the tax amount will automatically change to zero. All other properties will still to have tax automatically calculated.