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	$35.35	6.389%	$37.6085	$37.61	$37.60	$37.60
Purchase #2	$72.48	5.627%	$76.5584	$76.56	$76.55	$76.60
Purchase #3	$126.48	3.646%	$131.0915	$131.09	$131.10	$131.10
Purchase #4	$230.78	11.874%	$258.1828	$258.18	$258.20	$258.20
Purchase #5	$47.35	10.389%	$52.2692	$52.27	$52.25	$52.30
Purchase #6	$103.81	9.703%	$113.8827	$113.88	$113.90	$113.90
Purchase #7	$48.64	3.760%	$50.4689	$50.47	$50.45	$50.50
7 purchase totals =	$664.89		$720.0620	$720.06	$720.05	$720.20