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	$121.30	8.354%	$131.4334	$131.43	$131.45	$131.40
Purchase #2	$223.52	8.191%	$241.8285	$241.83	$241.85	$241.80
Purchase #3	$226.51	7.208%	$242.8368	$242.84	$242.85	$242.80
Purchase #4	$201.72	6.763%	$215.3623	$215.36	$215.35	$215.40
Purchase #5	$47.39	9.810%	$52.039	$52.04	$52.05	$52.00
Purchase #6	$117.89	7.447%	$126.6693	$126.67	$126.65	$126.70
Purchase #7	$150.83	7.617%	$162.3187	$162.32	$162.30	$162.30
7 purchase totals =	$1,089.16		$1,172.4880	$1,172.49	$1,172.50	$1,172.40