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	$192.27	12.848%	$216.9728	$216.97	$216.95	$217.00
Purchase #2	$116.52	12.644%	$131.2528	$131.25	$131.25	$131.30
Purchase #3	$24.59	12.812%	$27.7405	$27.74	$27.75	$27.70
Purchase #4	$103.43	12.587%	$116.4487	$116.45	$116.45	$116.40
Purchase #5	$127.46	8.423%	$138.196	$138.20	$138.20	$138.20
Purchase #6	$87.99	4.288%	$91.763	$91.76	$91.75	$91.80
Purchase #7	$48.63	3.764%	$50.4604	$50.46	$50.45	$50.50
7 purchase totals =	$700.89		$772.8342	$772.83	$772.80	$772.90