Enable for customer to remove reward, coupon or voucher values from cart/checkout

Hi!
If customer adds a coupon, reward or voucher at the Cart page (or during Checkout when using additional extension) there is no way for customer to remove this information if he wants to try out different options. The only way now is probably to remove the product from the cart and then start all over again.
How can I add option to remove or enter space/zero in these input fields, any suggestions?

BR
/Hackej