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	$54.35	10.118%	$59.8491	$59.85	$59.85	$59.80
Purchase #2	$228.94	5.287%	$241.0441	$241.04	$241.05	$241.00
Purchase #3	$168.56	13.149%	$190.724	$190.72	$190.70	$190.70
Purchase #4	$7.46	5.192%	$7.8473	$7.85	$7.85	$7.80
Purchase #5	$158.35	11.504%	$176.5666	$176.57	$176.55	$176.60
Purchase #6	$54.66	3.363%	$56.4982	$56.50	$56.50	$56.50
Purchase #7	$89.74	11.434%	$100.0009	$100.00	$100.00	$100.00
7 purchase totals =	$762.06		$832.5302	$832.53	$832.50	$832.40