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	$197.66	4.523%	$206.6002	$206.60	$206.60	$206.60
Purchase #2	$30.87	6.289%	$32.8114	$32.81	$32.80	$32.80
Purchase #3	$238.88	5.693%	$252.4794	$252.48	$252.50	$252.50
Purchase #4	$43.67	10.128%	$48.0929	$48.09	$48.10	$48.10
Purchase #5	$165.42	4.305%	$172.5413	$172.54	$172.55	$172.50
Purchase #6	$243.85	11.381%	$271.6026	$271.60	$271.60	$271.60
Purchase #7	$42.26	8.594%	$45.8918	$45.89	$45.90	$45.90
7 purchase totals =	$962.61		$1,030.0196	$1,030.01	$1,030.05	$1,030.00