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	$10.94	7.527%	$11.7635	$11.76	$11.75	$11.80
Purchase #2	$158.87	13.756%	$180.7242	$180.72	$180.70	$180.70
Purchase #3	$71.53	6.307%	$76.0414	$76.04	$76.05	$76.00
Purchase #4	$179.50	5.184%	$188.8053	$188.81	$188.80	$188.80
Purchase #5	$133.85	5.552%	$141.2814	$141.28	$141.30	$141.30
Purchase #6	$63.49	5.497%	$66.98	$66.98	$67.00	$67.00
Purchase #7	$82.58	8.126%	$89.2905	$89.29	$89.30	$89.30
7 purchase totals =	$700.76		$754.8863	$754.88	$754.90	$754.90