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	$43.63	10.646%	$48.2748	$48.27	$48.25	$48.30
Purchase #2	$151.26	9.367%	$165.4285	$165.43	$165.45	$165.40
Purchase #3	$31.60	8.238%	$34.2032	$34.20	$34.20	$34.20
Purchase #4	$144.41	5.641%	$152.5562	$152.56	$152.55	$152.60
Purchase #5	$125.83	11.127%	$139.8311	$139.83	$139.85	$139.80
Purchase #6	$130.89	9.671%	$143.5484	$143.55	$143.55	$143.50
Purchase #7	$18.65	13.297%	$21.1299	$21.13	$21.15	$21.10
7 purchase totals =	$646.27		$704.9721	$704.97	$705.00	$704.90