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	$41.50	13.461%	$47.0863	$47.09	$47.10	$47.10
Purchase #2	$19.60	11.751%	$21.9032	$21.90	$21.90	$21.90
Purchase #3	$30.71	9.472%	$33.6189	$33.62	$33.60	$33.60
Purchase #4	$51.51	5.631%	$54.4105	$54.41	$54.40	$54.40
Purchase #5	$235.28	11.575%	$262.5137	$262.51	$262.50	$262.50
Purchase #6	$240.42	13.475%	$272.8166	$272.82	$272.80	$272.80
Purchase #7	$230.83	6.543%	$245.9332	$245.93	$245.95	$245.90
7 purchase totals =	$849.85		$938.2824	$938.28	$938.25	$938.20