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	$147.99	10.860%	$164.0617	$164.06	$164.05	$164.10
Purchase #2	$78.80	11.114%	$87.5578	$87.56	$87.55	$87.60
Purchase #3	$133.95	11.692%	$149.6114	$149.61	$149.60	$149.60
Purchase #4	$48.52	7.112%	$51.9707	$51.97	$51.95	$52.00
Purchase #5	$60.29	5.422%	$63.5589	$63.56	$63.55	$63.60
Purchase #6	$125.47	13.836%	$142.83	$142.83	$142.85	$142.80
Purchase #7	$70.35	11.717%	$78.5929	$78.59	$78.60	$78.60
7 purchase totals =	$665.37		$738.1834	$738.18	$738.15	$738.30