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	$151.37	10.189%	$166.7931	$166.79	$166.80	$166.80
Purchase #2	$227.25	3.289%	$234.7243	$234.72	$234.70	$234.70
Purchase #3	$55.99	10.153%	$61.6747	$61.67	$61.65	$61.70
Purchase #4	$111.58	5.465%	$117.6778	$117.68	$117.70	$117.70
Purchase #5	$98.47	13.307%	$111.5734	$111.57	$111.55	$111.60
Purchase #6	$231.47	10.225%	$255.1378	$255.14	$255.15	$255.10
Purchase #7	$138.53	5.373%	$145.9732	$145.97	$145.95	$146.00
7 purchase totals =	$1,014.66		$1,093.5543	$1,093.54	$1,093.50	$1,093.60