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	$114.96	11.254%	$127.8976	$127.90	$127.90	$127.90
Purchase #2	$62.96	9.215%	$68.7618	$68.76	$68.75	$68.80
Purchase #3	$235.64	5.198%	$247.8886	$247.89	$247.90	$247.90
Purchase #4	$50.83	7.865%	$54.8278	$54.83	$54.85	$54.80
Purchase #5	$145.59	10.599%	$161.0211	$161.02	$161.00	$161.00
Purchase #6	$145.32	10.598%	$160.721	$160.72	$160.70	$160.70
Purchase #7	$243.27	3.642%	$252.1299	$252.13	$252.15	$252.10
7 purchase totals =	$998.57		$1,073.2478	$1,073.25	$1,073.25	$1,073.20