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	$208.30	7.184%	$223.2643	$223.26	$223.25	$223.30
Purchase #2	$144.81	6.575%	$154.3313	$154.33	$154.35	$154.30
Purchase #3	$170.61	11.462%	$190.1653	$190.17	$190.15	$190.20
Purchase #4	$213.90	9.700%	$234.6483	$234.65	$234.65	$234.60
Purchase #5	$83.25	9.513%	$91.1696	$91.17	$91.15	$91.20
Purchase #6	$40.49	11.496%	$45.1447	$45.14	$45.15	$45.10
Purchase #7	$213.96	5.574%	$225.8861	$225.89	$225.90	$225.90
7 purchase totals =	$1,075.32		$1,164.6096	$1,164.61	$1,164.60	$1,164.60