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	$100.82	10.365%	$111.27	$111.27	$111.25	$111.30
Purchase #2	$200.71	10.544%	$221.8729	$221.87	$221.85	$221.90
Purchase #3	$145.38	6.237%	$154.4474	$154.45	$154.45	$154.40
Purchase #4	$83.85	9.619%	$91.9155	$91.92	$91.90	$91.90
Purchase #5	$199.43	5.227%	$209.8542	$209.85	$209.85	$209.90
Purchase #6	$56.73	4.821%	$59.465	$59.47	$59.45	$59.50
Purchase #7	$194.65	11.652%	$217.3306	$217.33	$217.35	$217.30
7 purchase totals =	$981.57		$1,066.1556	$1,066.16	$1,066.10	$1,066.20