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	$212.44	6.829%	$226.9475	$226.95	$226.95	$226.90
Purchase #2	$241.83	11.580%	$269.8339	$269.83	$269.85	$269.80
Purchase #3	$19.94	6.347%	$21.2056	$21.21	$21.20	$21.20
Purchase #4	$85.96	5.626%	$90.7961	$90.80	$90.80	$90.80
Purchase #5	$61.77	12.470%	$69.4727	$69.47	$69.45	$69.50
Purchase #6	$101.94	6.545%	$108.612	$108.61	$108.60	$108.60
Purchase #7	$245.37	4.138%	$255.5234	$255.52	$255.50	$255.50
7 purchase totals =	$969.25		$1,042.3912	$1,042.39	$1,042.35	$1,042.30