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	$56.85	9.866%	$62.4588	$62.46	$62.45	$62.50
Purchase #2	$83.67	9.299%	$91.4505	$91.45	$91.45	$91.50
Purchase #3	$118.25	12.128%	$132.5914	$132.59	$132.60	$132.60
Purchase #4	$81.36	3.546%	$84.245	$84.25	$84.25	$84.20
Purchase #5	$62.41	8.579%	$67.7642	$67.76	$67.75	$67.80
Purchase #6	$227.77	7.780%	$245.4905	$245.49	$245.50	$245.50
Purchase #7	$179.27	9.558%	$196.4046	$196.40	$196.40	$196.40
7 purchase totals =	$809.58		$880.4050	$880.40	$880.40	$880.50