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	$177.50	13.342%	$201.1821	$201.18	$201.20	$201.20
Purchase #2	$114.52	12.219%	$128.5132	$128.51	$128.50	$128.50
Purchase #3	$143.87	4.866%	$150.8707	$150.87	$150.85	$150.90
Purchase #4	$114.95	10.709%	$127.26	$127.26	$127.25	$127.30
Purchase #5	$86.94	4.429%	$90.7906	$90.79	$90.80	$90.80
Purchase #6	$95.57	3.182%	$98.611	$98.61	$98.60	$98.60
Purchase #7	$190.89	10.238%	$210.4333	$210.43	$210.45	$210.40
7 purchase totals =	$924.24		$1,007.6609	$1,007.65	$1,007.65	$1,007.70