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	$214.57	12.316%	$240.9964	$241.00	$241.00	$241.00
Purchase #2	$168.40	10.492%	$186.0685	$186.07	$186.05	$186.10
Purchase #3	$35.86	13.120%	$40.5648	$40.56	$40.55	$40.60
Purchase #4	$155.68	11.541%	$173.647	$173.65	$173.65	$173.60
Purchase #5	$140.28	4.358%	$146.3934	$146.39	$146.40	$146.40
Purchase #6	$46.43	8.705%	$50.4717	$50.47	$50.45	$50.50
Purchase #7	$58.60	6.768%	$62.566	$62.57	$62.55	$62.60
7 purchase totals =	$819.82		$900.7078	$900.71	$900.65	$900.80