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	$222.34	13.416%	$252.1691	$252.17	$252.15	$252.20
Purchase #2	$41.69	8.599%	$45.2749	$45.27	$45.25	$45.30
Purchase #3	$73.37	12.594%	$82.6102	$82.61	$82.60	$82.60
Purchase #4	$242.50	6.421%	$258.0709	$258.07	$258.05	$258.10
Purchase #5	$104.38	6.733%	$111.4079	$111.41	$111.40	$111.40
Purchase #6	$131.72	13.580%	$149.6076	$149.61	$149.60	$149.60
Purchase #7	$133.84	10.287%	$147.6081	$147.61	$147.60	$147.60
7 purchase totals =	$949.84		$1,046.7487	$1,046.75	$1,046.65	$1,046.80