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	$92.53	7.787%	$99.7353	$99.74	$99.75	$99.70
Purchase #2	$60.34	7.466%	$64.845	$64.85	$64.85	$64.80
Purchase #3	$106.75	10.447%	$117.9022	$117.90	$117.90	$117.90
Purchase #4	$128.52	7.189%	$137.7593	$137.76	$137.75	$137.80
Purchase #5	$244.30	4.521%	$255.3448	$255.34	$255.35	$255.30
Purchase #6	$13.81	7.462%	$14.8405	$14.84	$14.85	$14.80
Purchase #7	$26.57	6.485%	$28.2931	$28.29	$28.30	$28.30
7 purchase totals =	$672.82		$718.7202	$718.72	$718.75	$718.60