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	$135.46	10.845%	$150.1506	$150.15	$150.15	$150.20
Purchase #2	$130.65	11.754%	$146.0066	$146.01	$146.00	$146.00
Purchase #3	$143.96	10.338%	$158.8426	$158.84	$158.85	$158.80
Purchase #4	$109.41	4.353%	$114.1726	$114.17	$114.15	$114.20
Purchase #5	$28.90	10.108%	$31.8212	$31.82	$31.80	$31.80
Purchase #6	$84.25	7.243%	$90.3522	$90.35	$90.35	$90.40
Purchase #7	$242.66	11.574%	$270.7455	$270.75	$270.75	$270.70
7 purchase totals =	$875.29		$962.0913	$962.09	$962.05	$962.10