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	$246.40	3.522%	$255.0782	$255.08	$255.10	$255.10
Purchase #2	$10.65	11.459%	$11.8704	$11.87	$11.85	$11.90
Purchase #3	$213.80	13.436%	$242.5262	$242.53	$242.55	$242.50
Purchase #4	$133.29	5.788%	$141.0048	$141.00	$141.00	$141.00
Purchase #5	$39.97	12.492%	$44.9631	$44.96	$44.95	$45.00
Purchase #6	$40.89	12.570%	$46.0299	$46.03	$46.05	$46.00
Purchase #7	$52.88	12.549%	$59.5159	$59.52	$59.50	$59.50
7 purchase totals =	$737.88		$800.9885	$800.99	$801.00	$801.00