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	$60.73	3.858%	$63.073	$63.07	$63.05	$63.10
Purchase #2	$163.64	12.769%	$184.5352	$184.54	$184.55	$184.50
Purchase #3	$73.51	6.548%	$78.3234	$78.32	$78.30	$78.30
Purchase #4	$111.58	3.214%	$115.1662	$115.17	$115.15	$115.20
Purchase #5	$236.42	5.714%	$249.929	$249.93	$249.95	$249.90
Purchase #6	$55.50	4.309%	$57.8915	$57.89	$57.90	$57.90
Purchase #7	$18.53	13.456%	$21.0234	$21.02	$21.00	$21.00
7 purchase totals =	$719.91		$769.9417	$769.94	$769.90	$769.90