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	$74.62	5.314%	$78.5853	$78.59	$78.60	$78.60
Purchase #2	$243.87	4.664%	$255.2441	$255.24	$255.25	$255.20
Purchase #3	$176.53	5.222%	$185.7484	$185.75	$185.75	$185.70
Purchase #4	$45.45	3.247%	$46.9258	$46.93	$46.95	$46.90
Purchase #5	$238.72	7.532%	$256.7004	$256.70	$256.70	$256.70
Purchase #6	$118.44	8.785%	$128.845	$128.85	$128.85	$128.80
Purchase #7	$139.45	4.514%	$145.7448	$145.74	$145.75	$145.70
7 purchase totals =	$1,037.08		$1,097.7938	$1,097.80	$1,097.85	$1,097.60