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	$49.85	8.246%	$53.9606	$53.96	$53.95	$54.00
Purchase #2	$121.77	13.712%	$138.4671	$138.47	$138.45	$138.50
Purchase #3	$244.57	4.671%	$255.9939	$255.99	$256.00	$256.00
Purchase #4	$176.57	6.652%	$188.3154	$188.32	$188.30	$188.30
Purchase #5	$43.98	3.443%	$45.4942	$45.49	$45.50	$45.50
Purchase #6	$33.54	4.383%	$35.0101	$35.01	$35.00	$35.00
Purchase #7	$40.43	13.619%	$45.9362	$45.94	$45.95	$45.90
7 purchase totals =	$710.71		$763.1775	$763.18	$763.15	$763.20