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	$100.83	10.322%	$111.2377	$111.24	$111.25	$111.20
Purchase #2	$241.89	5.176%	$254.4102	$254.41	$254.40	$254.40
Purchase #3	$33.87	3.808%	$35.1598	$35.16	$35.15	$35.20
Purchase #4	$192.57	10.344%	$212.4894	$212.49	$212.50	$212.50
Purchase #5	$87.44	13.403%	$99.1596	$99.16	$99.15	$99.20
Purchase #6	$87.98	8.607%	$95.5524	$95.55	$95.55	$95.60
Purchase #7	$140.86	10.388%	$155.4925	$155.49	$155.50	$155.50
7 purchase totals =	$885.44		$963.5016	$963.50	$963.50	$963.60