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	$38.80	13.224%	$43.9309	$43.93	$43.95	$43.90
Purchase #2	$195.81	4.749%	$205.109	$205.11	$205.10	$205.10
Purchase #3	$9.61	11.483%	$10.7135	$10.71	$10.70	$10.70
Purchase #4	$151.83	3.783%	$157.5737	$157.57	$157.55	$157.60
Purchase #5	$102.94	8.320%	$111.5046	$111.50	$111.50	$111.50
Purchase #6	$11.54	9.143%	$12.5951	$12.60	$12.60	$12.60
Purchase #7	$45.31	6.780%	$48.382	$48.38	$48.40	$48.40
7 purchase totals =	$555.84		$589.8088	$589.80	$589.80	$589.80