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	$83.54	12.109%	$93.6559	$93.66	$93.65	$93.70
Purchase #2	$103.43	7.559%	$111.2483	$111.25	$111.25	$111.20
Purchase #3	$134.78	5.472%	$142.1552	$142.16	$142.15	$142.20
Purchase #4	$61.92	6.451%	$65.9145	$65.91	$65.90	$65.90
Purchase #5	$177.61	6.675%	$189.4655	$189.47	$189.45	$189.50
Purchase #6	$144.78	3.298%	$149.5548	$149.55	$149.55	$149.60
Purchase #7	$103.83	10.570%	$114.8048	$114.80	$114.80	$114.80
7 purchase totals =	$809.89		$866.7990	$866.80	$866.75	$866.90