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	$225.62	5.690%	$238.4578	$238.46	$238.45	$238.50
Purchase #2	$199.54	4.281%	$208.0823	$208.08	$208.10	$208.10
Purchase #3	$190.89	9.249%	$208.5454	$208.55	$208.55	$208.50
Purchase #4	$119.83	10.784%	$132.7525	$132.75	$132.75	$132.80
Purchase #5	$44.42	6.398%	$47.262	$47.26	$47.25	$47.30
Purchase #6	$47.80	12.125%	$53.5958	$53.60	$53.60	$53.60
Purchase #7	$38.76	10.506%	$42.8321	$42.83	$42.85	$42.80
7 purchase totals =	$866.86		$931.5279	$931.53	$931.55	$931.60