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	$95.85	13.139%	$108.4437	$108.44	$108.45	$108.40
Purchase #2	$150.86	7.542%	$162.2379	$162.24	$162.25	$162.20
Purchase #3	$99.50	9.286%	$108.7396	$108.74	$108.75	$108.70
Purchase #4	$241.68	11.649%	$269.8333	$269.83	$269.85	$269.80
Purchase #5	$221.67	12.267%	$248.8623	$248.86	$248.85	$248.90
Purchase #6	$176.27	7.794%	$190.0085	$190.01	$190.00	$190.00
Purchase #7	$196.40	7.105%	$210.3542	$210.35	$210.35	$210.40
7 purchase totals =	$1,182.23		$1,298.4795	$1,298.47	$1,298.50	$1,298.40