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	$26.95	5.231%	$28.3598	$28.36	$28.35	$28.40
Purchase #2	$188.82	6.131%	$200.3966	$200.40	$200.40	$200.40
Purchase #3	$95.28	10.707%	$105.4816	$105.48	$105.50	$105.50
Purchase #4	$18.66	4.389%	$19.479	$19.48	$19.50	$19.50
Purchase #5	$192.94	9.176%	$210.6442	$210.64	$210.65	$210.60
Purchase #6	$48.43	7.490%	$52.0574	$52.06	$52.05	$52.10
Purchase #7	$137.55	9.831%	$151.0725	$151.07	$151.05	$151.10
7 purchase totals =	$708.63		$767.4911	$767.49	$767.50	$767.60