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	$108.48	5.688%	$114.6503	$114.65	$114.65	$114.70
Purchase #2	$109.88	12.257%	$123.348	$123.35	$123.35	$123.30
Purchase #3	$190.66	3.237%	$196.8317	$196.83	$196.85	$196.80
Purchase #4	$121.81	3.856%	$126.507	$126.51	$126.50	$126.50
Purchase #5	$49.84	12.346%	$55.9932	$55.99	$56.00	$56.00
Purchase #6	$83.60	7.525%	$89.8909	$89.89	$89.90	$89.90
Purchase #7	$250.35	3.783%	$259.8207	$259.82	$259.80	$259.80
7 purchase totals =	$914.62		$967.0418	$967.04	$967.05	$967.00