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	$10.85	9.136%	$11.8413	$11.84	$11.85	$11.80
Purchase #2	$154.55	9.198%	$168.7655	$168.77	$168.75	$168.80
Purchase #3	$41.46	5.719%	$43.8311	$43.83	$43.85	$43.80
Purchase #4	$160.65	10.510%	$177.5343	$177.53	$177.55	$177.50
Purchase #5	$243.93	3.757%	$253.0945	$253.09	$253.10	$253.10
Purchase #6	$182.52	7.840%	$196.8296	$196.83	$196.85	$196.80
Purchase #7	$127.42	12.792%	$143.7196	$143.72	$143.70	$143.70
7 purchase totals =	$921.38		$995.6159	$995.61	$995.65	$995.50