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	$10.73	8.203%	$11.6102	$11.61	$11.60	$11.60
Purchase #2	$205.86	4.223%	$214.5535	$214.55	$214.55	$214.60
Purchase #3	$100.67	3.462%	$104.1552	$104.16	$104.15	$104.20
Purchase #4	$16.72	11.808%	$18.6943	$18.69	$18.70	$18.70
Purchase #5	$222.94	3.844%	$231.5098	$231.51	$231.50	$231.50
Purchase #6	$184.64	5.140%	$194.1305	$194.13	$194.15	$194.10
Purchase #7	$228.96	3.744%	$237.5323	$237.53	$237.55	$237.50
7 purchase totals =	$970.52		$1,012.1858	$1,012.18	$1,012.20	$1,012.20