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	$126.38	5.151%	$132.8898	$132.89	$132.90	$132.90
Purchase #2	$106.44	8.185%	$115.1521	$115.15	$115.15	$115.20
Purchase #3	$44.45	4.636%	$46.5107	$46.51	$46.50	$46.50
Purchase #4	$67.86	7.324%	$72.8301	$72.83	$72.85	$72.80
Purchase #5	$249.59	6.487%	$265.7809	$265.78	$265.80	$265.80
Purchase #6	$172.99	13.734%	$196.7484	$196.75	$196.75	$196.70
Purchase #7	$214.86	10.547%	$237.5213	$237.52	$237.50	$237.50
7 purchase totals =	$982.57		$1,067.4333	$1,067.43	$1,067.45	$1,067.40