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	$164.84	12.725%	$185.8159	$185.82	$185.80	$185.80
Purchase #2	$40.77	7.488%	$43.8229	$43.82	$43.80	$43.80
Purchase #3	$100.86	10.222%	$111.1699	$111.17	$111.15	$111.20
Purchase #4	$11.86	8.130%	$12.8242	$12.82	$12.80	$12.80
Purchase #5	$87.78	7.311%	$94.1976	$94.20	$94.20	$94.20
Purchase #6	$76.25	10.785%	$84.4736	$84.47	$84.45	$84.50
Purchase #7	$174.58	5.258%	$183.7594	$183.76	$183.75	$183.80
7 purchase totals =	$656.94		$716.0635	$716.06	$715.95	$716.10