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	$87.27	8.131%	$94.3659	$94.37	$94.35	$94.40
Purchase #2	$41.30	13.119%	$46.7181	$46.72	$46.70	$46.70
Purchase #3	$127.79	13.490%	$145.0289	$145.03	$145.05	$145.00
Purchase #4	$131.27	5.530%	$138.5292	$138.53	$138.55	$138.50
Purchase #5	$48.78	13.117%	$55.1785	$55.18	$55.20	$55.20
Purchase #6	$56.62	5.659%	$59.8241	$59.82	$59.80	$59.80
Purchase #7	$212.37	12.295%	$238.4809	$238.48	$238.50	$238.50
7 purchase totals =	$705.40		$778.1256	$778.13	$778.15	$778.10