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	$122.31	6.184%	$129.8737	$129.87	$129.85	$129.90
Purchase #2	$241.61	4.568%	$252.6467	$252.65	$252.65	$252.60
Purchase #3	$40.55	11.691%	$45.2907	$45.29	$45.30	$45.30
Purchase #4	$220.68	3.550%	$228.5141	$228.51	$228.50	$228.50
Purchase #5	$95.79	4.457%	$100.0594	$100.06	$100.05	$100.10
Purchase #6	$101.32	4.447%	$105.8257	$105.83	$105.85	$105.80
Purchase #7	$149.72	13.255%	$169.5654	$169.57	$169.55	$169.60
7 purchase totals =	$971.98		$1,031.7757	$1,031.78	$1,031.75	$1,031.80