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	$168.56	13.271%	$190.9296	$190.93	$190.95	$190.90
Purchase #2	$141.89	11.687%	$158.4727	$158.47	$158.45	$158.50
Purchase #3	$56.50	4.735%	$59.1753	$59.18	$59.20	$59.20
Purchase #4	$62.95	7.214%	$67.4912	$67.49	$67.50	$67.50
Purchase #5	$90.87	12.311%	$102.057	$102.06	$102.05	$102.10
Purchase #6	$80.89	5.756%	$85.546	$85.55	$85.55	$85.50
Purchase #7	$18.48	8.146%	$19.9854	$19.99	$20.00	$20.00
7 purchase totals =	$620.14		$683.6572	$683.67	$683.70	$683.70