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	$157.47	10.521%	$174.0374	$174.04	$174.05	$174.00
Purchase #2	$81.32	5.829%	$86.0601	$86.06	$86.05	$86.10
Purchase #3	$208.86	6.651%	$222.7513	$222.75	$222.75	$222.80
Purchase #4	$111.39	13.205%	$126.099	$126.10	$126.10	$126.10
Purchase #5	$69.84	11.871%	$78.1307	$78.13	$78.15	$78.10
Purchase #6	$113.60	8.155%	$122.8641	$122.86	$122.85	$122.90
Purchase #7	$121.95	12.822%	$137.5864	$137.59	$137.60	$137.60
7 purchase totals =	$864.43		$947.5290	$947.53	$947.55	$947.60