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	$85.78	10.662%	$94.9259	$94.93	$94.95	$94.90
Purchase #2	$51.86	6.839%	$55.4067	$55.41	$55.40	$55.40
Purchase #3	$111.46	5.504%	$117.5948	$117.59	$117.60	$117.60
Purchase #4	$80.46	3.786%	$83.5062	$83.51	$83.50	$83.50
Purchase #5	$102.33	9.384%	$111.9326	$111.93	$111.95	$111.90
Purchase #6	$65.45	13.635%	$74.3741	$74.37	$74.35	$74.40
Purchase #7	$164.44	8.807%	$178.9222	$178.92	$178.90	$178.90
7 purchase totals =	$661.78		$716.6625	$716.66	$716.65	$716.60