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	$14.56	4.173%	$15.1676	$15.17	$15.15	$15.20
Purchase #2	$143.55	7.594%	$154.4512	$154.45	$154.45	$154.50
Purchase #3	$137.29	13.453%	$155.7596	$155.76	$155.75	$155.80
Purchase #4	$134.31	11.778%	$150.129	$150.13	$150.15	$150.10
Purchase #5	$241.59	8.464%	$262.0382	$262.04	$262.05	$262.00
Purchase #6	$117.82	4.863%	$123.5496	$123.55	$123.55	$123.50
Purchase #7	$178.26	9.236%	$194.7241	$194.72	$194.70	$194.70
7 purchase totals =	$967.38		$1,055.8193	$1,055.82	$1,055.80	$1,055.80