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	$206.66	7.712%	$222.5976	$222.60	$222.60	$222.60
Purchase #2	$87.42	5.399%	$92.1398	$92.14	$92.15	$92.10
Purchase #3	$15.97	8.240%	$17.2859	$17.29	$17.30	$17.30
Purchase #4	$96.84	13.124%	$109.5493	$109.55	$109.55	$109.50
Purchase #5	$127.98	11.778%	$143.0535	$143.05	$143.05	$143.10
Purchase #6	$41.83	11.148%	$46.4932	$46.49	$46.50	$46.50
Purchase #7	$172.53	5.770%	$182.485	$182.49	$182.50	$182.50
7 purchase totals =	$749.23		$813.6043	$813.61	$813.65	$813.60