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	$246.75	12.602%	$277.8454	$277.85	$277.85	$277.80
Purchase #2	$220.43	11.356%	$245.462	$245.46	$245.45	$245.50
Purchase #3	$52.39	4.304%	$54.6449	$54.64	$54.65	$54.60
Purchase #4	$242.60	6.684%	$258.8154	$258.82	$258.80	$258.80
Purchase #5	$91.47	9.682%	$100.3261	$100.33	$100.35	$100.30
Purchase #6	$155.71	8.245%	$168.5483	$168.55	$168.55	$168.50
Purchase #7	$244.47	6.627%	$260.671	$260.67	$260.65	$260.70
7 purchase totals =	$1,253.82		$1,366.3131	$1,366.32	$1,366.30	$1,366.20