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	$63.27	5.735%	$66.8985	$66.90	$66.90	$66.90
Purchase #2	$126.64	10.464%	$139.8916	$139.89	$139.90	$139.90
Purchase #3	$127.47	11.149%	$141.6816	$141.68	$141.70	$141.70
Purchase #4	$166.43	4.819%	$174.4503	$174.45	$174.45	$174.50
Purchase #5	$242.93	10.763%	$269.0766	$269.08	$269.10	$269.10
Purchase #6	$95.68	7.858%	$103.1985	$103.20	$103.20	$103.20
Purchase #7	$64.42	12.870%	$72.7109	$72.71	$72.70	$72.70
7 purchase totals =	$886.84		$967.9080	$967.91	$967.95	$968.00