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	$182.75	7.767%	$196.9442	$196.94	$196.95	$196.90
Purchase #2	$82.52	13.108%	$93.3367	$93.34	$93.35	$93.30
Purchase #3	$243.65	3.538%	$252.2703	$252.27	$252.25	$252.30
Purchase #4	$40.77	11.125%	$45.3057	$45.31	$45.30	$45.30
Purchase #5	$9.85	9.123%	$10.7486	$10.75	$10.75	$10.70
Purchase #6	$131.51	12.635%	$148.1263	$148.13	$148.15	$148.10
Purchase #7	$42.72	4.593%	$44.6821	$44.68	$44.70	$44.70
7 purchase totals =	$733.77		$791.4139	$791.42	$791.45	$791.30