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	$220.32	10.189%	$242.7684	$242.77	$242.75	$242.80
Purchase #2	$35.67	13.442%	$40.4648	$40.46	$40.45	$40.50
Purchase #3	$53.98	13.510%	$61.2727	$61.27	$61.25	$61.30
Purchase #4	$29.36	12.213%	$32.9457	$32.95	$32.95	$32.90
Purchase #5	$9.98	11.712%	$11.1489	$11.15	$11.15	$11.10
Purchase #6	$206.93	10.429%	$228.5107	$228.51	$228.50	$228.50
Purchase #7	$175.47	8.171%	$189.8077	$189.81	$189.80	$189.80
7 purchase totals =	$731.71		$806.9189	$806.92	$806.85	$806.90