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	$240.75	7.832%	$259.6055	$259.61	$259.60	$259.60
Purchase #2	$249.77	3.491%	$258.4895	$258.49	$258.50	$258.50
Purchase #3	$125.87	10.538%	$139.1342	$139.13	$139.15	$139.10
Purchase #4	$148.28	13.210%	$167.8678	$167.87	$167.85	$167.90
Purchase #5	$162.32	5.622%	$171.4456	$171.45	$171.45	$171.40
Purchase #6	$61.34	7.369%	$65.8601	$65.86	$65.85	$65.90
Purchase #7	$10.42	12.738%	$11.7473	$11.75	$11.75	$11.70
7 purchase totals =	$998.75		$1,074.1500	$1,074.16	$1,074.15	$1,074.10