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	$78.29	5.230%	$82.3846	$82.38	$82.40	$82.40
Purchase #2	$119.78	4.156%	$124.7581	$124.76	$124.75	$124.80
Purchase #3	$113.58	4.385%	$118.5605	$118.56	$118.55	$118.60
Purchase #4	$108.92	4.269%	$113.5698	$113.57	$113.55	$113.60
Purchase #5	$189.38	9.757%	$207.8578	$207.86	$207.85	$207.90
Purchase #6	$124.57	5.521%	$131.4475	$131.45	$131.45	$131.40
Purchase #7	$133.76	6.202%	$142.0558	$142.06	$142.05	$142.10
7 purchase totals =	$868.28		$920.6341	$920.64	$920.60	$920.80