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	$173.94	9.379%	$190.2538	$190.25	$190.25	$190.30
Purchase #2	$101.80	7.805%	$109.7455	$109.75	$109.75	$109.70
Purchase #3	$136.78	8.632%	$148.5868	$148.59	$148.60	$148.60
Purchase #4	$201.42	6.769%	$215.0541	$215.05	$215.05	$215.10
Purchase #5	$21.95	13.563%	$24.9271	$24.93	$24.95	$24.90
Purchase #6	$54.82	11.313%	$61.0218	$61.02	$61.00	$61.00
Purchase #7	$18.89	12.556%	$21.2618	$21.26	$21.25	$21.30
7 purchase totals =	$709.60		$770.8509	$770.85	$770.85	$770.90