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	$61.60	11.834%	$68.8897	$68.89	$68.90	$68.90
Purchase #2	$21.26	5.639%	$22.4589	$22.46	$22.45	$22.50
Purchase #3	$100.60	10.382%	$111.0443	$111.04	$111.05	$111.00
Purchase #4	$192.34	11.659%	$214.7649	$214.76	$214.75	$214.80
Purchase #5	$56.79	3.632%	$58.8526	$58.85	$58.85	$58.90
Purchase #6	$107.43	11.346%	$119.619	$119.62	$119.60	$119.60
Purchase #7	$19.60	11.208%	$21.7968	$21.80	$21.80	$21.80
7 purchase totals =	$559.62		$617.4262	$617.42	$617.40	$617.50