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	$210.47	5.821%	$222.7215	$222.72	$222.70	$222.70
Purchase #2	$209.73	13.467%	$237.9743	$237.97	$237.95	$238.00
Purchase #3	$208.98	6.515%	$222.595	$222.60	$222.60	$222.60
Purchase #4	$57.55	3.526%	$59.5792	$59.58	$59.60	$59.60
Purchase #5	$11.47	4.854%	$12.0268	$12.03	$12.05	$12.00
Purchase #6	$21.96	7.462%	$23.5987	$23.60	$23.60	$23.60
Purchase #7	$126.45	10.230%	$139.3858	$139.39	$139.40	$139.40
7 purchase totals =	$846.61		$917.8813	$917.89	$917.90	$917.90