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	$185.35	9.158%	$202.3244	$202.32	$202.30	$202.30
Purchase #2	$143.46	11.103%	$159.3884	$159.39	$159.40	$159.40
Purchase #3	$112.91	9.638%	$123.7923	$123.79	$123.80	$123.80
Purchase #4	$108.59	5.536%	$114.6015	$114.60	$114.60	$114.60
Purchase #5	$198.83	11.733%	$222.1587	$222.16	$222.15	$222.20
Purchase #6	$132.50	10.357%	$146.223	$146.22	$146.20	$146.20
Purchase #7	$104.83	8.806%	$114.0613	$114.06	$114.05	$114.10
7 purchase totals =	$986.47		$1,082.5496	$1,082.54	$1,082.50	$1,082.60