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	$58.55	11.232%	$65.1263	$65.13	$65.15	$65.10
Purchase #2	$8.41	4.269%	$8.769	$8.77	$8.75	$8.80
Purchase #3	$37.60	8.249%	$40.7016	$40.70	$40.70	$40.70
Purchase #4	$220.76	3.138%	$227.6874	$227.69	$227.70	$227.70
Purchase #5	$143.72	4.529%	$150.2291	$150.23	$150.25	$150.20
Purchase #6	$10.77	10.469%	$11.8975	$11.90	$11.90	$11.90
Purchase #7	$137.53	3.287%	$142.0506	$142.05	$142.05	$142.10
7 purchase totals =	$617.34		$646.4615	$646.47	$646.50	$646.50