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	$56.42	10.759%	$62.4902	$62.49	$62.50	$62.50
Purchase #2	$80.43	12.383%	$90.3896	$90.39	$90.40	$90.40
Purchase #3	$6.91	13.509%	$7.8435	$7.84	$7.85	$7.80
Purchase #4	$11.35	11.592%	$12.6657	$12.67	$12.65	$12.70
Purchase #5	$63.98	12.733%	$72.1266	$72.13	$72.15	$72.10
Purchase #6	$35.42	12.691%	$39.9152	$39.92	$39.90	$39.90
Purchase #7	$56.83	10.694%	$62.9074	$62.91	$62.90	$62.90
7 purchase totals =	$311.34		$348.3382	$348.35	$348.35	$348.30