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	$66.70	3.258%	$68.8731	$68.87	$68.85	$68.90
Purchase #2	$230.27	11.404%	$256.53	$256.53	$256.55	$256.50
Purchase #3	$182.94	7.213%	$196.1355	$196.14	$196.15	$196.10
Purchase #4	$136.43	5.333%	$143.7058	$143.71	$143.70	$143.70
Purchase #5	$113.70	3.843%	$118.0695	$118.07	$118.05	$118.10
Purchase #6	$138.65	12.541%	$156.0381	$156.04	$156.05	$156.00
Purchase #7	$5.28	4.700%	$5.5282	$5.53	$5.55	$5.50
7 purchase totals =	$873.97		$944.8802	$944.89	$944.90	$944.80