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	$184.95	8.469%	$200.6134	$200.61	$200.60	$200.60
Purchase #2	$140.89	3.554%	$145.8972	$145.90	$145.90	$145.90
Purchase #3	$113.51	12.161%	$127.314	$127.31	$127.30	$127.30
Purchase #4	$191.72	4.759%	$200.844	$200.84	$200.85	$200.80
Purchase #5	$41.88	12.847%	$47.2603	$47.26	$47.25	$47.30
Purchase #6	$128.54	10.870%	$142.5123	$142.51	$142.50	$142.50
Purchase #7	$110.61	3.472%	$114.4504	$114.45	$114.45	$114.50
7 purchase totals =	$912.10		$978.8916	$978.88	$978.85	$978.90