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	$82.52	9.714%	$90.536	$90.54	$90.55	$90.50
Purchase #2	$229.44	7.106%	$245.744	$245.74	$245.75	$245.70
Purchase #3	$119.69	6.186%	$127.094	$127.09	$127.10	$127.10
Purchase #4	$96.95	10.520%	$107.1491	$107.15	$107.15	$107.10
Purchase #5	$27.79	5.357%	$29.2787	$29.28	$29.30	$29.30
Purchase #6	$104.42	11.863%	$116.8073	$116.81	$116.80	$116.80
Purchase #7	$83.51	5.289%	$87.9268	$87.93	$87.95	$87.90
7 purchase totals =	$744.32		$804.5359	$804.54	$804.60	$804.40