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	$101.49	9.556%	$111.1884	$111.19	$111.20	$111.20
Purchase #2	$46.26	8.464%	$50.1754	$50.18	$50.20	$50.20
Purchase #3	$225.99	5.297%	$237.9607	$237.96	$237.95	$238.00
Purchase #4	$140.76	10.263%	$155.2062	$155.21	$155.20	$155.20
Purchase #5	$117.93	13.215%	$133.5144	$133.51	$133.50	$133.50
Purchase #6	$119.72	6.519%	$127.5245	$127.52	$127.50	$127.50
Purchase #7	$63.28	13.846%	$72.0417	$72.04	$72.05	$72.00
7 purchase totals =	$815.43		$887.6113	$887.61	$887.60	$887.60