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	$36.89	10.758%	$40.8586	$40.86	$40.85	$40.90
Purchase #2	$46.29	9.527%	$50.7	$50.70	$50.70	$50.70
Purchase #3	$91.87	3.455%	$95.0441	$95.04	$95.05	$95.00
Purchase #4	$193.98	5.472%	$204.5946	$204.59	$204.60	$204.60
Purchase #5	$171.61	7.210%	$183.9831	$183.98	$184.00	$184.00
Purchase #6	$124.38	12.471%	$139.8914	$139.89	$139.90	$139.90
Purchase #7	$217.78	4.430%	$227.4277	$227.43	$227.45	$227.40
7 purchase totals =	$882.80		$942.4995	$942.49	$942.55	$942.50