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	$225.86	13.260%	$255.809	$255.81	$255.80	$255.80
Purchase #2	$45.30	5.691%	$47.878	$47.88	$47.90	$47.90
Purchase #3	$26.63	11.508%	$29.6946	$29.69	$29.70	$29.70
Purchase #4	$206.49	5.348%	$217.5331	$217.53	$217.55	$217.50
Purchase #5	$58.66	5.453%	$61.8587	$61.86	$61.85	$61.90
Purchase #6	$111.38	8.481%	$120.8261	$120.83	$120.85	$120.80
Purchase #7	$78.56	10.660%	$86.9345	$86.93	$86.95	$86.90
7 purchase totals =	$752.88		$820.5340	$820.53	$820.60	$820.50