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	$41.48	10.826%	$45.9706	$45.97	$45.95	$46.00
Purchase #2	$34.43	3.195%	$35.53	$35.53	$35.55	$35.50
Purchase #3	$173.56	12.259%	$194.8367	$194.84	$194.85	$194.80
Purchase #4	$29.42	11.423%	$32.7806	$32.78	$32.80	$32.80
Purchase #5	$55.48	3.546%	$57.4473	$57.45	$57.45	$57.40
Purchase #6	$55.52	10.244%	$61.2075	$61.21	$61.20	$61.20
Purchase #7	$131.54	8.451%	$142.6564	$142.66	$142.65	$142.70
7 purchase totals =	$521.43		$570.4291	$570.44	$570.45	$570.40