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	$183.54	8.504%	$199.1482	$199.15	$199.15	$199.10
Purchase #2	$100.83	10.615%	$111.5331	$111.53	$111.55	$111.50
Purchase #3	$64.85	3.755%	$67.2851	$67.29	$67.30	$67.30
Purchase #4	$121.64	12.734%	$137.1296	$137.13	$137.15	$137.10
Purchase #5	$202.87	10.649%	$224.4736	$224.47	$224.45	$224.50
Purchase #6	$139.99	8.174%	$151.4328	$151.43	$151.45	$151.40
Purchase #7	$221.52	6.142%	$235.1258	$235.13	$235.15	$235.10
7 purchase totals =	$1,035.24		$1,126.1282	$1,126.13	$1,126.20	$1,126.00