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	$11.97	5.311%	$12.6057	$12.61	$12.60	$12.60
Purchase #2	$42.56	5.540%	$44.9178	$44.92	$44.90	$44.90
Purchase #3	$96.52	8.103%	$104.341	$104.34	$104.35	$104.30
Purchase #4	$53.89	11.433%	$60.0512	$60.05	$60.05	$60.10
Purchase #5	$35.49	6.674%	$37.8586	$37.86	$37.85	$37.90
Purchase #6	$114.28	5.168%	$120.186	$120.19	$120.20	$120.20
Purchase #7	$106.42	4.404%	$111.1067	$111.11	$111.10	$111.10
7 purchase totals =	$461.13		$491.0670	$491.08	$491.05	$491.10