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	$73.46	9.510%	$80.446	$80.45	$80.45	$80.40
Purchase #2	$69.61	7.462%	$74.8043	$74.80	$74.80	$74.80
Purchase #3	$213.90	11.667%	$238.8557	$238.86	$238.85	$238.90
Purchase #4	$144.61	11.444%	$161.1592	$161.16	$161.15	$161.20
Purchase #5	$65.45	12.275%	$73.484	$73.48	$73.50	$73.50
Purchase #6	$126.92	13.849%	$144.4972	$144.50	$144.50	$144.50
Purchase #7	$113.32	8.870%	$123.3715	$123.37	$123.35	$123.40
7 purchase totals =	$807.27		$896.6179	$896.62	$896.60	$896.70