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	$94.83	7.607%	$102.0437	$102.04	$102.05	$102.00
Purchase #2	$99.78	4.269%	$104.0396	$104.04	$104.05	$104.00
Purchase #3	$121.25	4.275%	$126.4334	$126.43	$126.45	$126.40
Purchase #4	$246.36	5.566%	$260.0724	$260.07	$260.05	$260.10
Purchase #5	$93.74	5.752%	$99.1319	$99.13	$99.15	$99.10
Purchase #6	$13.73	12.354%	$15.4262	$15.43	$15.45	$15.40
Purchase #7	$45.89	11.509%	$51.1715	$51.17	$51.15	$51.20
7 purchase totals =	$715.58		$758.3187	$758.31	$758.35	$758.20