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	$59.43	6.748%	$63.4403	$63.44	$63.45	$63.40
Purchase #2	$101.50	12.342%	$114.0271	$114.03	$114.05	$114.00
Purchase #3	$186.79	13.694%	$212.369	$212.37	$212.35	$212.40
Purchase #4	$33.31	12.509%	$37.4767	$37.48	$37.50	$37.50
Purchase #5	$89.84	12.311%	$100.9002	$100.90	$100.90	$100.90
Purchase #6	$112.98	12.830%	$127.4753	$127.48	$127.50	$127.50
Purchase #7	$118.44	6.864%	$126.5697	$126.57	$126.55	$126.60
7 purchase totals =	$702.29		$782.2583	$782.27	$782.30	$782.30