Is it possible to assign a tax rate against a product but for it to work in reverse. Let me explain...

So my prices already include tax where applicable (without tax rates being used in zen cart). Is there a way so that if I set 20% tax rate to a product that during checkout it displays what percentage of the price it is currently set. (as supposed to adding 20% on to the price).

Example, product price = £10
If tax set at 20%
Rather than zen then making total price £12, it keeps the price £10 and displays £10 of which £1.66 is tax?

If not I assume I'd have to deduct 20% from my product prices that tax applies? (which would be a pain)

Anyone a tax wizard that can advise best approach?

Cheers