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	$126.66	7.772%	$136.504	$136.50	$136.50	$136.50
Purchase #2	$29.80	6.296%	$31.6762	$31.68	$31.70	$31.70
Purchase #3	$140.32	8.246%	$151.8908	$151.89	$151.90	$151.90
Purchase #4	$84.34	12.644%	$95.0039	$95.00	$95.00	$95.00
Purchase #5	$225.64	10.615%	$249.5917	$249.59	$249.60	$249.60
Purchase #6	$240.41	6.407%	$255.8131	$255.81	$255.80	$255.80
Purchase #7	$136.29	10.310%	$150.3415	$150.34	$150.35	$150.30
7 purchase totals =	$983.46		$1,070.8212	$1,070.81	$1,070.85	$1,070.80