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	$138.32	10.166%	$152.3816	$152.38	$152.40	$152.40
Purchase #2	$112.85	3.484%	$116.7817	$116.78	$116.80	$116.80
Purchase #3	$54.93	9.330%	$60.055	$60.06	$60.05	$60.10
Purchase #4	$60.35	5.544%	$63.6958	$63.70	$63.70	$63.70
Purchase #5	$91.35	10.447%	$100.8933	$100.89	$100.90	$100.90
Purchase #6	$193.91	5.555%	$204.6817	$204.68	$204.70	$204.70
Purchase #7	$50.81	6.858%	$54.2945	$54.29	$54.30	$54.30
7 purchase totals =	$702.52		$752.7836	$752.78	$752.85	$752.90