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	$143.31	5.374%	$151.0115	$151.01	$151.00	$151.00
Purchase #2	$108.56	7.827%	$117.057	$117.06	$117.05	$117.10
Purchase #3	$52.75	7.733%	$56.8292	$56.83	$56.85	$56.80
Purchase #4	$157.68	9.373%	$172.4593	$172.46	$172.45	$172.50
Purchase #5	$159.55	9.785%	$175.162	$175.16	$175.15	$175.20
Purchase #6	$92.41	3.315%	$95.4734	$95.47	$95.45	$95.50
Purchase #7	$98.88	4.797%	$103.6233	$103.62	$103.60	$103.60
7 purchase totals =	$813.14		$871.6157	$871.61	$871.55	$871.70