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	$166.48	3.825%	$172.8479	$172.85	$172.85	$172.80
Purchase #2	$187.77	6.265%	$199.5338	$199.53	$199.55	$199.50
Purchase #3	$87.55	5.153%	$92.0615	$92.06	$92.05	$92.10
Purchase #4	$233.76	13.395%	$265.0722	$265.07	$265.05	$265.10
Purchase #5	$17.83	12.859%	$20.1228	$20.12	$20.10	$20.10
Purchase #6	$93.44	7.644%	$100.5826	$100.58	$100.60	$100.60
Purchase #7	$111.70	12.313%	$125.4536	$125.45	$125.45	$125.50
7 purchase totals =	$898.53		$975.6744	$975.66	$975.65	$975.70