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	$240.59	8.476%	$260.9824	$260.98	$261.00	$261.00
Purchase #2	$9.52	5.761%	$10.0684	$10.07	$10.05	$10.10
Purchase #3	$166.87	11.509%	$186.0751	$186.08	$186.10	$186.10
Purchase #4	$43.27	12.128%	$48.5178	$48.52	$48.50	$48.50
Purchase #5	$92.44	9.132%	$100.8816	$100.88	$100.90	$100.90
Purchase #6	$25.79	12.188%	$28.9333	$28.93	$28.95	$28.90
Purchase #7	$115.51	10.367%	$127.4849	$127.48	$127.50	$127.50
7 purchase totals =	$693.99		$762.9435	$762.94	$763.00	$763.00