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	$114.54	11.385%	$127.5804	$127.58	$127.60	$127.60
Purchase #2	$95.54	3.366%	$98.7559	$98.76	$98.75	$98.80
Purchase #3	$87.69	7.565%	$94.3237	$94.32	$94.30	$94.30
Purchase #4	$126.55	3.729%	$131.269	$131.27	$131.25	$131.30
Purchase #5	$176.87	5.817%	$187.1585	$187.16	$187.15	$187.20
Purchase #6	$181.85	10.429%	$200.8151	$200.82	$200.80	$200.80
Purchase #7	$92.89	8.495%	$100.781	$100.78	$100.80	$100.80
7 purchase totals =	$875.93		$940.6836	$940.69	$940.65	$940.80