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	$222.98	5.771%	$235.8482	$235.85	$235.85	$235.80
Purchase #2	$43.92	6.564%	$46.8029	$46.80	$46.80	$46.80
Purchase #3	$10.36	13.408%	$11.7491	$11.75	$11.75	$11.70
Purchase #4	$135.62	6.554%	$144.5085	$144.51	$144.50	$144.50
Purchase #5	$81.45	11.185%	$90.5602	$90.56	$90.55	$90.60
Purchase #6	$43.98	10.211%	$48.4708	$48.47	$48.45	$48.50
Purchase #7	$135.59	3.697%	$140.6028	$140.60	$140.60	$140.60
7 purchase totals =	$673.90		$718.5425	$718.54	$718.50	$718.50