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	$32.57	6.427%	$34.6633	$34.66	$34.65	$34.70
Purchase #2	$45.52	7.184%	$48.7902	$48.79	$48.80	$48.80
Purchase #3	$96.87	7.221%	$103.865	$103.87	$103.85	$103.90
Purchase #4	$100.67	11.528%	$112.2752	$112.28	$112.30	$112.30
Purchase #5	$229.60	13.771%	$261.2182	$261.22	$261.20	$261.20
Purchase #6	$163.39	13.407%	$185.2957	$185.30	$185.30	$185.30
Purchase #7	$137.75	10.185%	$151.7798	$151.78	$151.80	$151.80
7 purchase totals =	$806.37		$897.8874	$897.90	$897.90	$898.00