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	$84.36	9.780%	$92.6104	$92.61	$92.60	$92.60
Purchase #2	$121.27	5.391%	$127.8077	$127.81	$127.80	$127.80
Purchase #3	$27.56	4.783%	$28.8782	$28.88	$28.90	$28.90
Purchase #4	$35.83	8.283%	$38.7978	$38.80	$38.80	$38.80
Purchase #5	$76.99	11.449%	$85.8046	$85.80	$85.80	$85.80
Purchase #6	$33.55	6.184%	$35.6247	$35.62	$35.60	$35.60
Purchase #7	$16.51	5.182%	$17.3655	$17.37	$17.35	$17.40
7 purchase totals =	$396.07		$426.8889	$426.89	$426.85	$426.90