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	$158.70	7.707%	$170.931	$170.93	$170.95	$170.90
Purchase #2	$189.78	3.319%	$196.0788	$196.08	$196.10	$196.10
Purchase #3	$141.27	5.807%	$149.4735	$149.47	$149.45	$149.50
Purchase #4	$58.57	7.641%	$63.0453	$63.05	$63.05	$63.00
Purchase #5	$91.45	10.297%	$100.8666	$100.87	$100.85	$100.90
Purchase #6	$102.68	13.449%	$116.4894	$116.49	$116.50	$116.50
Purchase #7	$111.44	7.199%	$119.4626	$119.46	$119.45	$119.50
7 purchase totals =	$853.89		$916.3472	$916.35	$916.35	$916.40