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	$90.62	11.127%	$100.7033	$100.70	$100.70	$100.70
Purchase #2	$119.98	5.422%	$126.4853	$126.49	$126.50	$126.50
Purchase #3	$108.95	6.186%	$115.6896	$115.69	$115.70	$115.70
Purchase #4	$68.68	13.666%	$78.0658	$78.07	$78.05	$78.10
Purchase #5	$90.70	5.135%	$95.3574	$95.36	$95.35	$95.40
Purchase #6	$187.89	11.709%	$209.89	$209.89	$209.90	$209.90
Purchase #7	$36.57	6.523%	$38.9555	$38.96	$38.95	$39.00
7 purchase totals =	$703.39		$765.1469	$765.16	$765.15	$765.30