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	$134.60	13.388%	$152.6202	$152.62	$152.60	$152.60
Purchase #2	$86.52	13.759%	$98.4243	$98.42	$98.40	$98.40
Purchase #3	$149.78	13.367%	$169.8011	$169.80	$169.80	$169.80
Purchase #4	$161.58	3.588%	$167.3775	$167.38	$167.40	$167.40
Purchase #5	$102.84	8.181%	$111.2533	$111.25	$111.25	$111.30
Purchase #6	$132.41	7.737%	$142.6546	$142.65	$142.65	$142.70
Purchase #7	$102.84	13.521%	$116.745	$116.75	$116.75	$116.70
7 purchase totals =	$870.57		$958.8760	$958.87	$958.85	$958.90