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	$223.47	9.557%	$244.827	$244.83	$244.85	$244.80
Purchase #2	$40.28	13.772%	$45.8274	$45.83	$45.85	$45.80
Purchase #3	$178.50	5.366%	$188.0783	$188.08	$188.10	$188.10
Purchase #4	$12.35	6.435%	$13.1447	$13.14	$13.15	$13.10
Purchase #5	$93.32	6.720%	$99.5911	$99.59	$99.60	$99.60
Purchase #6	$238.71	8.841%	$259.8144	$259.81	$259.80	$259.80
Purchase #7	$49.26	7.581%	$52.9944	$52.99	$53.00	$53.00
7 purchase totals =	$835.89		$904.2773	$904.27	$904.35	$904.20