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	$37.59	8.667%	$40.8479	$40.85	$40.85	$40.80
Purchase #2	$91.27	10.465%	$100.8214	$100.82	$100.80	$100.80
Purchase #3	$117.53	7.224%	$126.0204	$126.02	$126.00	$126.00
Purchase #4	$208.54	11.866%	$233.2854	$233.29	$233.30	$233.30
Purchase #5	$226.40	5.396%	$238.6165	$238.62	$238.60	$238.60
Purchase #6	$51.59	6.142%	$54.7587	$54.76	$54.75	$54.80
Purchase #7	$99.71	4.674%	$104.3704	$104.37	$104.35	$104.40
7 purchase totals =	$832.63		$898.7207	$898.73	$898.65	$898.70