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	$136.63	10.238%	$150.6182	$150.62	$150.60	$150.60
Purchase #2	$94.38	5.307%	$99.3887	$99.39	$99.40	$99.40
Purchase #3	$191.64	8.806%	$208.5158	$208.52	$208.50	$208.50
Purchase #4	$69.96	4.857%	$73.358	$73.36	$73.35	$73.40
Purchase #5	$199.39	4.496%	$208.3546	$208.35	$208.35	$208.40
Purchase #6	$89.32	3.763%	$92.6811	$92.68	$92.70	$92.70
Purchase #7	$59.34	4.749%	$62.1581	$62.16	$62.15	$62.20
7 purchase totals =	$840.66		$895.0745	$895.08	$895.05	$895.20