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	$158.60	13.403%	$179.8572	$179.86	$179.85	$179.90
Purchase #2	$183.33	13.626%	$208.3105	$208.31	$208.30	$208.30
Purchase #3	$43.55	9.703%	$47.7757	$47.78	$47.80	$47.80
Purchase #4	$113.72	10.485%	$125.6435	$125.64	$125.65	$125.60
Purchase #5	$182.82	3.476%	$189.1748	$189.17	$189.15	$189.20
Purchase #6	$104.77	6.733%	$111.8242	$111.82	$111.80	$111.80
Purchase #7	$226.37	7.136%	$242.5238	$242.52	$242.50	$242.50
7 purchase totals =	$1,013.16		$1,105.1097	$1,105.10	$1,105.05	$1,105.10