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	$180.83	13.337%	$204.9473	$204.95	$204.95	$204.90
Purchase #2	$111.43	4.266%	$116.1836	$116.18	$116.20	$116.20
Purchase #3	$117.91	9.307%	$128.8839	$128.88	$128.90	$128.90
Purchase #4	$121.33	4.261%	$126.4999	$126.50	$126.50	$126.50
Purchase #5	$59.50	4.638%	$62.2596	$62.26	$62.25	$62.30
Purchase #6	$200.65	4.776%	$210.233	$210.23	$210.25	$210.20
Purchase #7	$153.52	10.476%	$169.6028	$169.60	$169.60	$169.60
7 purchase totals =	$945.17		$1,018.6101	$1,018.60	$1,018.65	$1,018.60