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	$153.34	3.352%	$158.48	$158.48	$158.50	$158.50
Purchase #2	$172.66	4.776%	$180.9062	$180.91	$180.90	$180.90
Purchase #3	$49.50	13.118%	$55.9934	$55.99	$56.00	$56.00
Purchase #4	$62.29	6.103%	$66.0916	$66.09	$66.10	$66.10
Purchase #5	$201.88	10.212%	$222.496	$222.50	$222.50	$222.50
Purchase #6	$187.84	6.378%	$199.8204	$199.82	$199.80	$199.80
Purchase #7	$228.52	13.182%	$258.6435	$258.64	$258.65	$258.60
7 purchase totals =	$1,056.03		$1,142.4311	$1,142.43	$1,142.45	$1,142.40