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	$212.73	8.689%	$231.2141	$231.21	$231.20	$231.20
Purchase #2	$126.85	3.246%	$130.9676	$130.97	$130.95	$131.00
Purchase #3	$199.61	4.454%	$208.5006	$208.50	$208.50	$208.50
Purchase #4	$108.89	5.142%	$114.4891	$114.49	$114.50	$114.50
Purchase #5	$31.42	8.604%	$34.1234	$34.12	$34.10	$34.10
Purchase #6	$92.59	6.807%	$98.8926	$98.89	$98.90	$98.90
Purchase #7	$104.59	6.434%	$111.3193	$111.32	$111.30	$111.30
7 purchase totals =	$876.68		$929.5067	$929.50	$929.45	$929.50