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	$138.48	9.141%	$151.1385	$151.14	$151.15	$151.10
Purchase #2	$99.87	5.224%	$105.0872	$105.09	$105.10	$105.10
Purchase #3	$83.85	5.788%	$88.7032	$88.70	$88.70	$88.70
Purchase #4	$93.62	6.266%	$99.4862	$99.49	$99.50	$99.50
Purchase #5	$188.84	5.822%	$199.8343	$199.83	$199.85	$199.80
Purchase #6	$179.68	3.389%	$185.7694	$185.77	$185.75	$185.80
Purchase #7	$135.73	12.294%	$152.4166	$152.42	$152.40	$152.40
7 purchase totals =	$920.07		$982.4354	$982.44	$982.45	$982.40