Price rounding should have the option to include tax

For UK businesses tax is added into the product price, when using the rounding price function in webstores items can be rounded up to say £14.00 but then the price shown on the site is not rounded as tax is added on top.

So for an item rounded to £14.00 the price shown on site will be £16.80. We would like to be able to round this to £17.00