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	$11.68	11.574%	$13.0318	$13.03	$13.05	$13.00
Purchase #2	$185.28	5.212%	$194.9368	$194.94	$194.95	$194.90
Purchase #3	$39.39	10.828%	$43.6551	$43.66	$43.65	$43.70
Purchase #4	$185.72	5.301%	$195.565	$195.57	$195.55	$195.60
Purchase #5	$239.34	4.403%	$249.8781	$249.88	$249.90	$249.90
Purchase #6	$168.28	13.421%	$190.8649	$190.86	$190.85	$190.90
Purchase #7	$173.27	8.195%	$187.4695	$187.47	$187.45	$187.50
7 purchase totals =	$1,002.96		$1,075.4012	$1,075.41	$1,075.40	$1,075.50