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	$235.83	13.344%	$267.2992	$267.30	$267.30	$267.30
Purchase #2	$128.83	12.723%	$145.221	$145.22	$145.20	$145.20
Purchase #3	$108.63	9.782%	$119.2562	$119.26	$119.25	$119.30
Purchase #4	$123.29	11.847%	$137.8962	$137.90	$137.90	$137.90
Purchase #5	$138.30	11.765%	$154.571	$154.57	$154.55	$154.60
Purchase #6	$187.47	6.594%	$199.8318	$199.83	$199.85	$199.80
Purchase #7	$153.53	12.631%	$172.9224	$172.92	$172.90	$172.90
7 purchase totals =	$1,075.88		$1,196.9978	$1,197.00	$1,196.95	$1,197.00