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	$240.72	6.318%	$255.9287	$255.93	$255.95	$255.90
Purchase #2	$105.39	11.639%	$117.6563	$117.66	$117.65	$117.70
Purchase #3	$190.44	7.794%	$205.2829	$205.28	$205.30	$205.30
Purchase #4	$179.80	4.183%	$187.321	$187.32	$187.30	$187.30
Purchase #5	$27.94	3.867%	$29.0204	$29.02	$29.00	$29.00
Purchase #6	$41.57	5.456%	$43.8381	$43.84	$43.85	$43.80
Purchase #7	$41.43	4.732%	$43.3905	$43.39	$43.40	$43.40
7 purchase totals =	$827.29		$882.4379	$882.44	$882.45	$882.40