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	$158.72	5.274%	$167.0909	$167.09	$167.10	$167.10
Purchase #2	$11.98	10.698%	$13.2616	$13.26	$13.25	$13.30
Purchase #3	$229.36	5.709%	$242.4542	$242.45	$242.45	$242.50
Purchase #4	$92.78	7.136%	$99.4008	$99.40	$99.40	$99.40
Purchase #5	$91.85	8.562%	$99.7142	$99.71	$99.70	$99.70
Purchase #6	$249.31	13.855%	$283.8519	$283.85	$283.85	$283.90
Purchase #7	$48.94	3.210%	$50.511	$50.51	$50.50	$50.50
7 purchase totals =	$882.94		$956.2846	$956.27	$956.25	$956.40