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	$61.53	3.598%	$63.7438	$63.74	$63.75	$63.70
Purchase #2	$72.82	11.600%	$81.2671	$81.27	$81.25	$81.30
Purchase #3	$63.50	4.723%	$66.4991	$66.50	$66.50	$66.50
Purchase #4	$19.88	3.845%	$20.6444	$20.64	$20.65	$20.60
Purchase #5	$238.31	9.231%	$260.3084	$260.31	$260.30	$260.30
Purchase #6	$39.84	7.791%	$42.9439	$42.94	$42.95	$42.90
Purchase #7	$39.47	10.517%	$43.6211	$43.62	$43.60	$43.60
7 purchase totals =	$535.35		$579.0278	$579.02	$579.00	$578.90