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	$65.41	9.482%	$71.6122	$71.61	$71.60	$71.60
Purchase #2	$148.36	9.874%	$163.0091	$163.01	$163.00	$163.00
Purchase #3	$210.71	8.296%	$228.1905	$228.19	$228.20	$228.20
Purchase #4	$240.78	6.243%	$255.8119	$255.81	$255.80	$255.80
Purchase #5	$171.60	11.682%	$191.6463	$191.65	$191.65	$191.60
Purchase #6	$115.96	13.377%	$131.472	$131.47	$131.45	$131.50
Purchase #7	$104.63	6.316%	$111.2384	$111.24	$111.25	$111.20
7 purchase totals =	$1,057.45		$1,152.9804	$1,152.98	$1,152.95	$1,152.90