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	$126.84	7.829%	$136.7703	$136.77	$136.75	$136.80
Purchase #2	$187.66	5.732%	$198.4167	$198.42	$198.40	$198.40
Purchase #3	$183.39	11.136%	$203.8123	$203.81	$203.80	$203.80
Purchase #4	$178.29	12.308%	$200.2339	$200.23	$200.25	$200.20
Purchase #5	$177.75	4.359%	$185.4981	$185.50	$185.50	$185.50
Purchase #6	$139.50	8.871%	$151.875	$151.88	$151.90	$151.90
Purchase #7	$139.84	6.141%	$148.4276	$148.43	$148.45	$148.40
7 purchase totals =	$1,133.27		$1,225.0339	$1,225.04	$1,225.05	$1,225.00