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	$196.41	11.139%	$218.2881	$218.29	$218.30	$218.30
Purchase #2	$189.67	12.866%	$214.0729	$214.07	$214.05	$214.10
Purchase #3	$45.39	7.534%	$48.8097	$48.81	$48.80	$48.80
Purchase #4	$40.56	11.323%	$45.1526	$45.15	$45.15	$45.20
Purchase #5	$163.88	5.619%	$173.0884	$173.09	$173.10	$173.10
Purchase #6	$91.77	12.504%	$103.2449	$103.24	$103.25	$103.20
Purchase #7	$136.54	6.366%	$145.2321	$145.23	$145.25	$145.20
7 purchase totals =	$864.22		$947.8887	$947.88	$947.90	$947.90