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	$184.45	4.211%	$192.2172	$192.22	$192.20	$192.20
Purchase #2	$201.27	3.638%	$208.5922	$208.59	$208.60	$208.60
Purchase #3	$102.92	9.271%	$112.4617	$112.46	$112.45	$112.50
Purchase #4	$150.39	9.866%	$165.2275	$165.23	$165.25	$165.20
Purchase #5	$52.38	13.262%	$59.3266	$59.33	$59.35	$59.30
Purchase #6	$17.45	10.375%	$19.2604	$19.26	$19.25	$19.30
Purchase #7	$222.29	8.764%	$241.7715	$241.77	$241.75	$241.80
7 purchase totals =	$931.15		$998.8571	$998.86	$998.85	$998.90