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	$143.60	6.440%	$152.8478	$152.85	$152.85	$152.80
Purchase #2	$70.47	9.297%	$77.0216	$77.02	$77.00	$77.00
Purchase #3	$63.87	6.164%	$67.8069	$67.81	$67.80	$67.80
Purchase #4	$201.69	10.302%	$222.4681	$222.47	$222.45	$222.50
Purchase #5	$48.30	13.596%	$54.8669	$54.87	$54.85	$54.90
Purchase #6	$209.41	13.429%	$237.5317	$237.53	$237.55	$237.50
Purchase #7	$12.76	13.460%	$14.4775	$14.48	$14.50	$14.50
7 purchase totals =	$750.10		$827.0205	$827.03	$827.00	$827.00