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	$139.65	9.416%	$152.7994	$152.80	$152.80	$152.80
Purchase #2	$139.37	10.376%	$153.831	$153.83	$153.85	$153.80
Purchase #3	$124.67	10.628%	$137.9199	$137.92	$137.90	$137.90
Purchase #4	$94.50	6.717%	$100.8476	$100.85	$100.85	$100.80
Purchase #5	$145.72	8.195%	$157.6618	$157.66	$157.65	$157.70
Purchase #6	$165.95	4.782%	$173.8857	$173.89	$173.90	$173.90
Purchase #7	$229.27	3.448%	$237.1752	$237.18	$237.20	$237.20
7 purchase totals =	$1,039.13		$1,114.1206	$1,114.13	$1,114.15	$1,114.10