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	$192.75	13.756%	$219.2647	$219.26	$219.25	$219.30
Purchase #2	$82.33	7.725%	$88.69	$88.69	$88.70	$88.70
Purchase #3	$171.64	8.310%	$185.9033	$185.90	$185.90	$185.90
Purchase #4	$106.89	3.872%	$111.0288	$111.03	$111.05	$111.00
Purchase #5	$95.30	13.862%	$108.5105	$108.51	$108.50	$108.50
Purchase #6	$14.31	4.137%	$14.902	$14.90	$14.90	$14.90
Purchase #7	$166.57	6.142%	$176.8007	$176.80	$176.80	$176.80
7 purchase totals =	$829.79		$905.1000	$905.09	$905.10	$905.10