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	$197.75	12.632%	$222.7298	$222.73	$222.75	$222.70
Purchase #2	$155.41	11.643%	$173.5044	$173.50	$173.50	$173.50
Purchase #3	$142.92	8.165%	$154.5894	$154.59	$154.60	$154.60
Purchase #4	$182.52	9.838%	$200.4763	$200.48	$200.50	$200.50
Purchase #5	$190.44	9.469%	$208.4728	$208.47	$208.45	$208.50
Purchase #6	$107.49	11.548%	$119.9029	$119.90	$119.90	$119.90
Purchase #7	$205.87	11.821%	$230.2059	$230.21	$230.20	$230.20
7 purchase totals =	$1,182.40		$1,309.8815	$1,309.88	$1,309.90	$1,309.90