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	$243.35	5.385%	$256.4544	$256.45	$256.45	$256.50
Purchase #2	$90.66	9.523%	$99.2936	$99.29	$99.30	$99.30
Purchase #3	$76.26	9.785%	$83.722	$83.72	$83.70	$83.70
Purchase #4	$221.51	7.688%	$238.5397	$238.54	$238.55	$238.50
Purchase #5	$62.94	9.623%	$68.9967	$69.00	$69.00	$69.00
Purchase #6	$39.82	13.210%	$45.0802	$45.08	$45.10	$45.10
Purchase #7	$142.95	5.563%	$150.9023	$150.90	$150.90	$150.90
7 purchase totals =	$877.49		$942.9889	$942.98	$943.00	$943.00