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	$50.52	5.677%	$53.388	$53.39	$53.40	$53.40
Purchase #2	$174.83	11.147%	$194.3183	$194.32	$194.30	$194.30
Purchase #3	$127.68	10.713%	$141.3584	$141.36	$141.35	$141.40
Purchase #4	$232.86	5.765%	$246.2844	$246.28	$246.30	$246.30
Purchase #5	$172.85	5.871%	$182.998	$183.00	$183.00	$183.00
Purchase #6	$42.39	6.350%	$45.0818	$45.08	$45.10	$45.10
Purchase #7	$91.29	10.410%	$100.7933	$100.79	$100.80	$100.80
7 purchase totals =	$892.42		$964.2222	$964.22	$964.25	$964.30