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	$224.71	7.456%	$241.4644	$241.46	$241.45	$241.50
Purchase #2	$35.73	13.610%	$40.5929	$40.59	$40.60	$40.60
Purchase #3	$46.37	5.245%	$48.8021	$48.80	$48.80	$48.80
Purchase #4	$11.98	7.250%	$12.8486	$12.85	$12.85	$12.80
Purchase #5	$124.47	5.342%	$131.1192	$131.12	$131.10	$131.10
Purchase #6	$147.66	8.589%	$160.3425	$160.34	$160.35	$160.30
Purchase #7	$81.73	12.834%	$92.2192	$92.22	$92.20	$92.20
7 purchase totals =	$672.65		$727.3889	$727.38	$727.35	$727.30