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	$127.78	9.376%	$139.7607	$139.76	$139.75	$139.80
Purchase #2	$119.83	5.542%	$126.471	$126.47	$126.45	$126.50
Purchase #3	$114.53	11.366%	$127.5475	$127.55	$127.55	$127.50
Purchase #4	$182.50	5.286%	$192.147	$192.15	$192.15	$192.10
Purchase #5	$66.75	8.480%	$72.4104	$72.41	$72.40	$72.40
Purchase #6	$45.87	11.712%	$51.2423	$51.24	$51.25	$51.20
Purchase #7	$12.65	10.575%	$13.9877	$13.99	$14.00	$14.00
7 purchase totals =	$669.91		$723.5666	$723.57	$723.55	$723.50