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	$214.91	5.128%	$225.9306	$225.93	$225.95	$225.90
Purchase #2	$144.79	12.246%	$162.521	$162.52	$162.50	$162.50
Purchase #3	$209.94	4.538%	$219.4671	$219.47	$219.45	$219.50
Purchase #4	$100.57	3.280%	$103.8687	$103.87	$103.85	$103.90
Purchase #5	$217.45	7.363%	$233.4608	$233.46	$233.45	$233.50
Purchase #6	$12.36	5.158%	$12.9975	$13.00	$13.00	$13.00
Purchase #7	$14.50	11.722%	$16.1997	$16.20	$16.20	$16.20
7 purchase totals =	$914.52		$974.4454	$974.45	$974.40	$974.50