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	$186.61	12.407%	$209.7627	$209.76	$209.75	$209.80
Purchase #2	$119.35	6.197%	$126.7461	$126.75	$126.75	$126.70
Purchase #3	$91.31	13.811%	$103.9208	$103.92	$103.90	$103.90
Purchase #4	$83.42	4.756%	$87.3875	$87.39	$87.40	$87.40
Purchase #5	$53.32	11.556%	$59.4817	$59.48	$59.50	$59.50
Purchase #6	$166.92	8.201%	$180.6091	$180.61	$180.60	$180.60
Purchase #7	$172.29	11.456%	$192.0275	$192.03	$192.05	$192.00
7 purchase totals =	$873.22		$959.9354	$959.94	$959.95	$959.90