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	$155.82	11.403%	$173.5882	$173.59	$173.60	$173.60
Purchase #2	$204.29	9.103%	$222.8865	$222.89	$222.90	$222.90
Purchase #3	$66.85	8.159%	$72.3043	$72.30	$72.30	$72.30
Purchase #4	$197.61	10.698%	$218.7503	$218.75	$218.75	$218.80
Purchase #5	$108.82	3.699%	$112.8453	$112.85	$112.85	$112.80
Purchase #6	$46.81	10.430%	$51.6923	$51.69	$51.70	$51.70
Purchase #7	$182.53	5.800%	$193.1167	$193.12	$193.10	$193.10
7 purchase totals =	$962.73		$1,045.1836	$1,045.19	$1,045.20	$1,045.20