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	$42.56	4.757%	$44.5846	$44.58	$44.60	$44.60
Purchase #2	$74.73	11.749%	$83.51	$83.51	$83.50	$83.50
Purchase #3	$238.81	12.105%	$267.718	$267.72	$267.70	$267.70
Purchase #4	$28.65	10.264%	$31.5906	$31.59	$31.60	$31.60
Purchase #5	$224.84	10.362%	$248.1379	$248.14	$248.15	$248.10
Purchase #6	$173.77	9.602%	$190.4554	$190.46	$190.45	$190.50
Purchase #7	$244.67	3.474%	$253.1698	$253.17	$253.15	$253.20
7 purchase totals =	$1,028.03		$1,119.1663	$1,119.17	$1,119.15	$1,119.20