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	$118.92	13.454%	$134.9195	$134.92	$134.90	$134.90
Purchase #2	$10.80	4.679%	$11.3053	$11.31	$11.30	$11.30
Purchase #3	$146.39	12.455%	$164.6229	$164.62	$164.60	$164.60
Purchase #4	$205.77	12.398%	$231.2814	$231.28	$231.30	$231.30
Purchase #5	$171.34	11.815%	$191.5838	$191.58	$191.60	$191.60
Purchase #6	$232.67	9.856%	$255.602	$255.60	$255.60	$255.60
Purchase #7	$164.92	8.406%	$178.7832	$178.78	$178.80	$178.80
7 purchase totals =	$1,050.81		$1,168.0981	$1,168.09	$1,168.10	$1,168.10