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	$59.53	8.505%	$64.593	$64.59	$64.60	$64.60
Purchase #2	$100.51	6.667%	$107.211	$107.21	$107.20	$107.20
Purchase #3	$80.76	13.620%	$91.7595	$91.76	$91.75	$91.80
Purchase #4	$10.87	6.743%	$11.603	$11.60	$11.60	$11.60
Purchase #5	$59.38	5.840%	$62.8478	$62.85	$62.85	$62.80
Purchase #6	$140.45	7.710%	$151.2787	$151.28	$151.30	$151.30
Purchase #7	$10.34	4.414%	$10.7964	$10.80	$10.80	$10.80
7 purchase totals =	$461.84		$500.0894	$500.09	$500.10	$500.10