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	$170.29	9.150%	$185.8715	$185.87	$185.85	$185.90
Purchase #2	$94.58	5.751%	$100.0193	$100.02	$100.00	$100.00
Purchase #3	$6.45	11.484%	$7.1907	$7.19	$7.20	$7.20
Purchase #4	$46.57	6.233%	$49.4727	$49.47	$49.45	$49.50
Purchase #5	$122.96	13.574%	$139.6506	$139.65	$139.65	$139.70
Purchase #6	$55.58	13.515%	$63.0916	$63.09	$63.10	$63.10
Purchase #7	$134.79	11.670%	$150.52	$150.52	$150.50	$150.50
7 purchase totals =	$631.22		$695.8164	$695.81	$695.75	$695.90