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	$69.55	7.619%	$74.849	$74.85	$74.85	$74.80
Purchase #2	$177.53	11.505%	$197.9548	$197.95	$197.95	$198.00
Purchase #3	$111.87	4.223%	$116.5943	$116.59	$116.60	$116.60
Purchase #4	$197.66	11.246%	$219.8888	$219.89	$219.90	$219.90
Purchase #5	$225.85	12.537%	$254.1648	$254.16	$254.15	$254.20
Purchase #6	$121.56	4.855%	$127.4617	$127.46	$127.45	$127.50
Purchase #7	$81.59	13.108%	$92.2848	$92.28	$92.30	$92.30
7 purchase totals =	$985.61		$1,083.1982	$1,083.18	$1,083.20	$1,083.30