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	$205.38	4.561%	$214.7474	$214.75	$214.75	$214.70
Purchase #2	$153.86	13.549%	$174.7065	$174.71	$174.70	$174.70
Purchase #3	$129.41	6.520%	$137.8475	$137.85	$137.85	$137.80
Purchase #4	$130.28	10.441%	$143.8825	$143.88	$143.90	$143.90
Purchase #5	$35.67	4.716%	$37.3522	$37.35	$37.35	$37.40
Purchase #6	$12.47	8.231%	$13.4964	$13.50	$13.50	$13.50
Purchase #7	$80.61	5.605%	$85.1282	$85.13	$85.15	$85.10
7 purchase totals =	$747.68		$807.1607	$807.17	$807.20	$807.10