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	$149.47	11.337%	$166.4154	$166.42	$166.40	$166.40
Purchase #2	$131.47	10.533%	$145.3177	$145.32	$145.30	$145.30
Purchase #3	$122.88	7.513%	$132.112	$132.11	$132.10	$132.10
Purchase #4	$46.42	11.117%	$51.5805	$51.58	$51.60	$51.60
Purchase #5	$242.70	7.476%	$260.8443	$260.84	$260.85	$260.80
Purchase #6	$72.38	8.482%	$78.5193	$78.52	$78.50	$78.50
Purchase #7	$56.44	8.126%	$61.0263	$61.03	$61.05	$61.00
7 purchase totals =	$821.76		$895.8155	$895.82	$895.80	$895.70