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	$188.41	5.729%	$199.204	$199.20	$199.20	$199.20
Purchase #2	$102.90	8.464%	$111.6095	$111.61	$111.60	$111.60
Purchase #3	$151.35	4.467%	$158.1108	$158.11	$158.10	$158.10
Purchase #4	$32.40	10.141%	$35.6857	$35.69	$35.70	$35.70
Purchase #5	$213.77	13.443%	$242.5071	$242.51	$242.50	$242.50
Purchase #6	$155.88	3.164%	$160.812	$160.81	$160.80	$160.80
Purchase #7	$211.38	13.580%	$240.0854	$240.09	$240.10	$240.10
7 purchase totals =	$1,056.09		$1,148.0145	$1,148.02	$1,148.00	$1,148.00