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	$200.69	11.184%	$223.1352	$223.14	$223.15	$223.10
Purchase #2	$74.79	13.751%	$85.0744	$85.07	$85.05	$85.10
Purchase #3	$90.51	5.590%	$95.5695	$95.57	$95.55	$95.60
Purchase #4	$136.91	3.641%	$141.8949	$141.89	$141.90	$141.90
Purchase #5	$87.78	5.667%	$92.7545	$92.75	$92.75	$92.80
Purchase #6	$18.87	8.612%	$20.4951	$20.50	$20.50	$20.50
Purchase #7	$157.91	10.325%	$174.2142	$174.21	$174.20	$174.20
7 purchase totals =	$767.46		$833.1378	$833.13	$833.10	$833.20