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	$169.65	12.623%	$191.0649	$191.06	$191.05	$191.10
Purchase #2	$103.85	13.225%	$117.5842	$117.58	$117.60	$117.60
Purchase #3	$135.72	13.747%	$154.3774	$154.38	$154.40	$154.40
Purchase #4	$121.27	5.732%	$128.2212	$128.22	$128.20	$128.20
Purchase #5	$43.85	3.717%	$45.4799	$45.48	$45.50	$45.50
Purchase #6	$93.69	7.487%	$100.7046	$100.70	$100.70	$100.70
Purchase #7	$67.41	4.271%	$70.2891	$70.29	$70.30	$70.30
7 purchase totals =	$735.44		$807.7213	$807.71	$807.75	$807.80