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	$224.49	9.748%	$246.3733	$246.37	$246.35	$246.40
Purchase #2	$126.25	13.347%	$143.1006	$143.10	$143.10	$143.10
Purchase #3	$84.75	9.151%	$92.5055	$92.51	$92.50	$92.50
Purchase #4	$155.32	8.726%	$168.8732	$168.87	$168.85	$168.90
Purchase #5	$116.25	6.319%	$123.5958	$123.60	$123.60	$123.60
Purchase #6	$151.36	3.507%	$156.6682	$156.67	$156.65	$156.70
Purchase #7	$134.42	11.512%	$149.8944	$149.89	$149.90	$149.90
7 purchase totals =	$992.84		$1,081.0110	$1,081.01	$1,080.95	$1,081.10