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	$104.86	11.524%	$116.9441	$116.94	$116.95	$116.90
Purchase #2	$56.89	4.507%	$59.454	$59.45	$59.45	$59.50
Purchase #3	$139.46	10.478%	$154.0726	$154.07	$154.05	$154.10
Purchase #4	$122.72	13.282%	$139.0197	$139.02	$139.00	$139.00
Purchase #5	$202.83	3.748%	$210.4321	$210.43	$210.45	$210.40
Purchase #6	$50.99	6.251%	$54.1774	$54.18	$54.20	$54.20
Purchase #7	$121.47	9.791%	$133.3631	$133.36	$133.35	$133.40
7 purchase totals =	$799.22		$867.4630	$867.45	$867.45	$867.50