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	$219.53	8.553%	$238.3064	$238.31	$238.30	$238.30
Purchase #2	$34.68	7.602%	$37.3164	$37.32	$37.30	$37.30
Purchase #3	$17.91	10.797%	$19.8437	$19.84	$19.85	$19.80
Purchase #4	$73.51	11.598%	$82.0357	$82.04	$82.05	$82.00
Purchase #5	$148.93	10.392%	$164.4068	$164.41	$164.40	$164.40
Purchase #6	$122.82	13.159%	$138.9819	$138.98	$139.00	$139.00
Purchase #7	$200.86	12.373%	$225.7124	$225.71	$225.70	$225.70
7 purchase totals =	$818.24		$906.6033	$906.61	$906.60	$906.50