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	$94.98	5.127%	$99.8496	$99.85	$99.85	$99.80
Purchase #2	$111.61	5.126%	$117.3311	$117.33	$117.35	$117.30
Purchase #3	$134.75	13.420%	$152.8335	$152.83	$152.85	$152.80
Purchase #4	$93.57	5.770%	$98.969	$98.97	$98.95	$99.00
Purchase #5	$117.47	12.771%	$132.4721	$132.47	$132.45	$132.50
Purchase #6	$116.28	13.567%	$132.0557	$132.06	$132.05	$132.10
Purchase #7	$199.86	13.598%	$227.037	$227.04	$227.05	$227.00
7 purchase totals =	$868.52		$960.5480	$960.55	$960.55	$960.50