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	$42.41	6.276%	$45.0717	$45.07	$45.05	$45.10
Purchase #2	$26.57	6.548%	$28.3098	$28.31	$28.30	$28.30
Purchase #3	$24.78	10.161%	$27.2979	$27.30	$27.30	$27.30
Purchase #4	$56.93	5.128%	$59.8494	$59.85	$59.85	$59.80
Purchase #5	$7.46	5.440%	$7.8658	$7.87	$7.85	$7.90
Purchase #6	$198.31	12.449%	$222.9976	$223.00	$223.00	$223.00
Purchase #7	$246.77	10.542%	$272.7845	$272.78	$272.80	$272.80
7 purchase totals =	$603.23		$664.1767	$664.18	$664.15	$664.20