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	$241.67	5.724%	$255.5032	$255.50	$255.50	$255.50
Purchase #2	$54.90	8.312%	$59.4633	$59.46	$59.45	$59.50
Purchase #3	$228.26	13.744%	$259.6321	$259.63	$259.65	$259.60
Purchase #4	$198.64	4.626%	$207.8291	$207.83	$207.85	$207.80
Purchase #5	$46.42	8.814%	$50.5115	$50.51	$50.50	$50.50
Purchase #6	$67.80	11.584%	$75.654	$75.65	$75.65	$75.70
Purchase #7	$176.90	6.189%	$187.8483	$187.85	$187.85	$187.80
7 purchase totals =	$1,014.59		$1,096.4415	$1,096.43	$1,096.45	$1,096.40