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	$66.60	8.661%	$72.3682	$72.37	$72.35	$72.40
Purchase #2	$46.38	4.544%	$48.4875	$48.49	$48.50	$48.50
Purchase #3	$153.50	3.253%	$158.4934	$158.49	$158.50	$158.50
Purchase #4	$140.78	13.344%	$159.5657	$159.57	$159.55	$159.60
Purchase #5	$153.93	11.648%	$171.8598	$171.86	$171.85	$171.90
Purchase #6	$231.83	9.506%	$253.8678	$253.87	$253.85	$253.90
Purchase #7	$126.55	13.773%	$143.9797	$143.98	$144.00	$144.00
7 purchase totals =	$919.57		$1,008.6221	$1,008.63	$1,008.60	$1,008.80