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	$65.68	7.205%	$70.4122	$70.41	$70.40	$70.40
Purchase #2	$82.61	8.852%	$89.9226	$89.92	$89.90	$89.90
Purchase #3	$145.39	5.828%	$153.8633	$153.86	$153.85	$153.90
Purchase #4	$125.52	10.804%	$139.0812	$139.08	$139.10	$139.10
Purchase #5	$212.26	13.843%	$241.6432	$241.64	$241.65	$241.60
Purchase #6	$108.45	8.686%	$117.87	$117.87	$117.85	$117.90
Purchase #7	$136.29	10.227%	$150.2284	$150.23	$150.25	$150.20
7 purchase totals =	$876.20		$963.0209	$963.01	$963.00	$963.00