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	$145.72	6.751%	$155.5576	$155.56	$155.55	$155.60
Purchase #2	$208.48	13.602%	$236.8374	$236.84	$236.85	$236.80
Purchase #3	$120.89	5.641%	$127.7094	$127.71	$127.70	$127.70
Purchase #4	$248.99	4.722%	$260.7473	$260.75	$260.75	$260.70
Purchase #5	$72.66	10.224%	$80.0888	$80.09	$80.10	$80.10
Purchase #6	$127.95	8.710%	$139.0944	$139.09	$139.10	$139.10
Purchase #7	$88.83	10.868%	$98.484	$98.48	$98.50	$98.50
7 purchase totals =	$1,013.52		$1,098.5189	$1,098.52	$1,098.55	$1,098.50