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	$138.57	9.222%	$151.3489	$151.35	$151.35	$151.30
Purchase #2	$132.89	13.768%	$151.1863	$151.19	$151.20	$151.20
Purchase #3	$150.62	10.548%	$166.5074	$166.51	$166.50	$166.50
Purchase #4	$100.35	3.601%	$103.9636	$103.96	$103.95	$104.00
Purchase #5	$220.67	13.327%	$250.0787	$250.08	$250.10	$250.10
Purchase #6	$230.45	11.451%	$256.8388	$256.84	$256.85	$256.80
Purchase #7	$83.88	10.685%	$92.8426	$92.84	$92.85	$92.80
7 purchase totals =	$1,057.43		$1,172.7663	$1,172.77	$1,172.80	$1,172.70