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	$216.60	8.111%	$234.1684	$234.17	$234.15	$234.20
Purchase #2	$78.86	8.258%	$85.3723	$85.37	$85.35	$85.40
Purchase #3	$180.45	10.601%	$199.5795	$199.58	$199.60	$199.60
Purchase #4	$65.65	10.647%	$72.6398	$72.64	$72.65	$72.60
Purchase #5	$221.26	11.105%	$245.8309	$245.83	$245.85	$245.80
Purchase #6	$228.42	4.473%	$238.6372	$238.64	$238.65	$238.60
Purchase #7	$13.60	12.160%	$15.2538	$15.25	$15.25	$15.30
7 purchase totals =	$1,004.84		$1,091.4819	$1,091.48	$1,091.50	$1,091.50