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	$62.72	5.661%	$66.2706	$66.27	$66.25	$66.30
Purchase #2	$64.46	3.848%	$66.9404	$66.94	$66.95	$66.90
Purchase #3	$11.93	11.496%	$13.3015	$13.30	$13.30	$13.30
Purchase #4	$60.50	9.705%	$66.3715	$66.37	$66.35	$66.40
Purchase #5	$88.48	10.317%	$97.6085	$97.61	$97.60	$97.60
Purchase #6	$238.70	5.526%	$251.8906	$251.89	$251.90	$251.90
Purchase #7	$49.98	10.341%	$55.1484	$55.15	$55.15	$55.10
7 purchase totals =	$576.77		$617.5315	$617.53	$617.50	$617.50