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	$119.95	9.706%	$131.5923	$131.59	$131.60	$131.60
Purchase #2	$60.52	4.859%	$63.4607	$63.46	$63.45	$63.50
Purchase #3	$142.35	7.815%	$153.4747	$153.47	$153.45	$153.50
Purchase #4	$242.66	10.620%	$268.4305	$268.43	$268.45	$268.40
Purchase #5	$172.64	9.451%	$188.9562	$188.96	$188.95	$189.00
Purchase #6	$185.83	3.330%	$192.0181	$192.02	$192.00	$192.00
Purchase #7	$12.31	13.230%	$13.9386	$13.94	$13.95	$13.90
7 purchase totals =	$936.26		$1,011.8711	$1,011.87	$1,011.85	$1,011.90