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	$232.43	11.538%	$259.2478	$259.25	$259.25	$259.20
Purchase #2	$221.84	8.836%	$241.4418	$241.44	$241.45	$241.40
Purchase #3	$64.82	4.197%	$67.5405	$67.54	$67.55	$67.50
Purchase #4	$33.74	3.452%	$34.9047	$34.90	$34.90	$34.90
Purchase #5	$18.54	5.364%	$19.5345	$19.53	$19.55	$19.50
Purchase #6	$127.84	4.393%	$133.456	$133.46	$133.45	$133.50
Purchase #7	$63.64	4.507%	$66.5083	$66.51	$66.50	$66.50
7 purchase totals =	$762.85		$822.6336	$822.63	$822.65	$822.50