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	$243.75	13.478%	$276.6026	$276.60	$276.60	$276.60
Purchase #2	$103.53	7.264%	$111.0504	$111.05	$111.05	$111.10
Purchase #3	$98.46	10.554%	$108.8515	$108.85	$108.85	$108.90
Purchase #4	$113.45	12.160%	$127.2455	$127.25	$127.25	$127.20
Purchase #5	$29.70	7.208%	$31.8408	$31.84	$31.85	$31.80
Purchase #6	$232.88	9.490%	$254.9803	$254.98	$255.00	$255.00
Purchase #7	$100.48	13.503%	$114.0478	$114.05	$114.05	$114.00
7 purchase totals =	$922.25		$1,024.6189	$1,024.62	$1,024.65	$1,024.60