Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$240.62	3.733%	$249.6023	$249.60	$249.60	$249.60
Purchase #2	$88.81	6.580%	$94.6537	$94.65	$94.65	$94.70
Purchase #3	$6.64	3.637%	$6.8815	$6.88	$6.90	$6.90
Purchase #4	$200.54	12.712%	$226.0326	$226.03	$226.05	$226.00
Purchase #5	$68.60	11.546%	$76.5206	$76.52	$76.50	$76.50
Purchase #6	$126.69	3.705%	$131.3839	$131.38	$131.40	$131.40
Purchase #7	$104.81	6.225%	$111.3344	$111.33	$111.35	$111.30
7 purchase totals =	$836.71		$896.4090	$896.39	$896.45	$896.40