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	$94.52	6.246%	$100.4237	$100.42	$100.40	$100.40
Purchase #2	$107.66	6.624%	$114.7914	$114.79	$114.80	$114.80
Purchase #3	$67.68	9.308%	$73.9797	$73.98	$74.00	$74.00
Purchase #4	$138.83	9.248%	$151.669	$151.67	$151.65	$151.70
Purchase #5	$115.28	6.702%	$123.0061	$123.01	$123.00	$123.00
Purchase #6	$196.87	12.623%	$221.7209	$221.72	$221.70	$221.70
Purchase #7	$210.51	8.590%	$228.5928	$228.59	$228.60	$228.60
7 purchase totals =	$931.35		$1,014.1836	$1,014.18	$1,014.15	$1,014.20