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	$90.57	13.775%	$103.046	$103.05	$103.05	$103.00
Purchase #2	$91.63	8.193%	$99.1372	$99.14	$99.15	$99.10
Purchase #3	$182.46	5.429%	$192.3658	$192.37	$192.35	$192.40
Purchase #4	$208.61	11.135%	$231.8387	$231.84	$231.85	$231.80
Purchase #5	$78.82	6.463%	$83.9141	$83.91	$83.90	$83.90
Purchase #6	$66.82	4.509%	$69.8329	$69.83	$69.85	$69.80
Purchase #7	$102.65	11.357%	$114.308	$114.31	$114.30	$114.30
7 purchase totals =	$821.56		$894.4427	$894.45	$894.45	$894.30