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	$104.62	6.528%	$111.4496	$111.45	$111.45	$111.40
Purchase #2	$28.69	11.284%	$31.9274	$31.93	$31.95	$31.90
Purchase #3	$157.82	3.196%	$162.8639	$162.86	$162.85	$162.90
Purchase #4	$55.77	7.871%	$60.1597	$60.16	$60.15	$60.20
Purchase #5	$12.53	5.330%	$13.1978	$13.20	$13.20	$13.20
Purchase #6	$94.52	4.651%	$98.9161	$98.92	$98.90	$98.90
Purchase #7	$11.80	6.534%	$12.571	$12.57	$12.55	$12.60
7 purchase totals =	$465.75		$491.0855	$491.09	$491.05	$491.10