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	$78.94	8.554%	$85.6925	$85.69	$85.70	$85.70
Purchase #2	$53.84	9.769%	$59.0996	$59.10	$59.10	$59.10
Purchase #3	$29.25	8.351%	$31.6927	$31.69	$31.70	$31.70
Purchase #4	$9.46	5.604%	$9.9901	$9.99	$10.00	$10.00
Purchase #5	$42.82	8.563%	$46.4867	$46.49	$46.50	$46.50
Purchase #6	$27.42	4.146%	$28.5568	$28.56	$28.55	$28.60
Purchase #7	$243.42	5.106%	$255.849	$255.85	$255.85	$255.80
7 purchase totals =	$485.15		$517.3674	$517.37	$517.40	$517.40