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	$177.52	11.107%	$197.2371	$197.24	$197.25	$197.20
Purchase #2	$244.59	10.583%	$270.475	$270.48	$270.50	$270.50
Purchase #3	$202.39	4.169%	$210.8276	$210.83	$210.85	$210.80
Purchase #4	$83.82	13.418%	$95.067	$95.07	$95.05	$95.10
Purchase #5	$126.32	13.559%	$143.4477	$143.45	$143.45	$143.40
Purchase #6	$34.45	8.792%	$37.4788	$37.48	$37.50	$37.50
Purchase #7	$50.69	8.456%	$54.9763	$54.98	$55.00	$55.00
7 purchase totals =	$919.78		$1,009.5095	$1,009.53	$1,009.60	$1,009.50