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	$225.39	5.521%	$237.8338	$237.83	$237.85	$237.80
Purchase #2	$37.94	3.671%	$39.3328	$39.33	$39.35	$39.30
Purchase #3	$13.85	4.710%	$14.5023	$14.50	$14.50	$14.50
Purchase #4	$146.77	8.820%	$159.7151	$159.72	$159.70	$159.70
Purchase #5	$36.81	7.312%	$39.5015	$39.50	$39.50	$39.50
Purchase #6	$103.94	13.325%	$117.79	$117.79	$117.80	$117.80
Purchase #7	$95.46	10.289%	$105.2819	$105.28	$105.30	$105.30
7 purchase totals =	$660.16		$713.9574	$713.95	$714.00	$713.90