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	$112.85	3.472%	$116.7682	$116.77	$116.75	$116.80
Purchase #2	$59.74	11.282%	$66.4799	$66.48	$66.50	$66.50
Purchase #3	$136.80	9.265%	$149.4745	$149.47	$149.45	$149.50
Purchase #4	$38.59	5.621%	$40.7591	$40.76	$40.75	$40.80
Purchase #5	$54.44	9.211%	$59.4545	$59.45	$59.45	$59.50
Purchase #6	$147.67	4.178%	$153.8397	$153.84	$153.85	$153.80
Purchase #7	$63.60	10.745%	$70.4338	$70.43	$70.45	$70.40
7 purchase totals =	$613.69		$657.2097	$657.20	$657.20	$657.30