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	$143.53	13.221%	$162.5061	$162.51	$162.50	$162.50
Purchase #2	$68.36	3.536%	$70.7772	$70.78	$70.80	$70.80
Purchase #3	$41.38	10.102%	$45.5602	$45.56	$45.55	$45.60
Purchase #4	$22.54	4.247%	$23.4973	$23.50	$23.50	$23.50
Purchase #5	$199.57	4.667%	$208.8839	$208.88	$208.90	$208.90
Purchase #6	$18.98	7.749%	$20.4508	$20.45	$20.45	$20.50
Purchase #7	$168.27	11.261%	$187.2189	$187.22	$187.20	$187.20
7 purchase totals =	$662.63		$718.8944	$718.90	$718.90	$719.00