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	$202.54	6.873%	$216.4606	$216.46	$216.45	$216.50
Purchase #2	$100.60	11.163%	$111.83	$111.83	$111.85	$111.80
Purchase #3	$194.85	7.696%	$209.8457	$209.85	$209.85	$209.80
Purchase #4	$31.93	8.548%	$34.6594	$34.66	$34.65	$34.70
Purchase #5	$116.43	8.478%	$126.3009	$126.30	$126.30	$126.30
Purchase #6	$20.40	3.473%	$21.1085	$21.11	$21.10	$21.10
Purchase #7	$154.83	13.702%	$176.0448	$176.04	$176.05	$176.00
7 purchase totals =	$821.58		$896.2499	$896.25	$896.25	$896.20