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	$241.62	10.325%	$266.5673	$266.57	$266.55	$266.60
Purchase #2	$48.69	12.181%	$54.6209	$54.62	$54.60	$54.60
Purchase #3	$100.39	4.384%	$104.7911	$104.79	$104.80	$104.80
Purchase #4	$53.25	11.146%	$59.1852	$59.19	$59.20	$59.20
Purchase #5	$25.78	12.733%	$29.0626	$29.06	$29.05	$29.10
Purchase #6	$143.53	5.449%	$151.3509	$151.35	$151.35	$151.40
Purchase #7	$138.28	7.703%	$148.9317	$148.93	$148.95	$148.90
7 purchase totals =	$751.54		$814.5097	$814.51	$814.50	$814.60