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	$136.84	4.379%	$142.8322	$142.83	$142.85	$142.80
Purchase #2	$71.75	5.666%	$75.8154	$75.82	$75.80	$75.80
Purchase #3	$100.72	10.758%	$111.5555	$111.56	$111.55	$111.60
Purchase #4	$123.90	7.720%	$133.4651	$133.47	$133.45	$133.50
Purchase #5	$177.42	4.215%	$184.8983	$184.90	$184.90	$184.90
Purchase #6	$159.85	5.302%	$168.3252	$168.33	$168.35	$168.30
Purchase #7	$95.66	3.324%	$98.8397	$98.84	$98.85	$98.80
7 purchase totals =	$866.14		$915.7314	$915.75	$915.75	$915.70