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	$247.72	11.331%	$275.7892	$275.79	$275.80	$275.80
Purchase #2	$177.34	4.421%	$185.1802	$185.18	$185.20	$185.20
Purchase #3	$104.52	6.832%	$111.6608	$111.66	$111.65	$111.70
Purchase #4	$124.91	13.509%	$141.7841	$141.78	$141.80	$141.80
Purchase #5	$41.32	4.797%	$43.3021	$43.30	$43.30	$43.30
Purchase #6	$190.84	3.667%	$197.8381	$197.84	$197.85	$197.80
Purchase #7	$173.81	13.500%	$197.2744	$197.27	$197.25	$197.30
7 purchase totals =	$1,060.46		$1,152.8289	$1,152.82	$1,152.85	$1,152.90