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	$58.51	10.657%	$64.7454	$64.75	$64.75	$64.70
Purchase #2	$78.77	12.758%	$88.8195	$88.82	$88.80	$88.80
Purchase #3	$222.34	11.154%	$247.1398	$247.14	$247.15	$247.10
Purchase #4	$107.39	5.391%	$113.1794	$113.18	$113.20	$113.20
Purchase #5	$126.27	10.185%	$139.1306	$139.13	$139.15	$139.10
Purchase #6	$128.76	3.327%	$133.0438	$133.04	$133.05	$133.00
Purchase #7	$246.39	11.857%	$275.6045	$275.60	$275.60	$275.60
7 purchase totals =	$968.43		$1,061.6630	$1,061.66	$1,061.70	$1,061.50