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	$236.97	8.196%	$256.3921	$256.39	$256.40	$256.40
Purchase #2	$123.65	3.476%	$127.9481	$127.95	$127.95	$127.90
Purchase #3	$22.60	6.347%	$24.0344	$24.03	$24.05	$24.00
Purchase #4	$154.26	11.503%	$172.0045	$172.00	$172.00	$172.00
Purchase #5	$93.42	9.629%	$102.4154	$102.42	$102.40	$102.40
Purchase #6	$207.86	9.762%	$228.1513	$228.15	$228.15	$228.20
Purchase #7	$166.48	5.387%	$175.4483	$175.45	$175.45	$175.40
7 purchase totals =	$1,005.24		$1,086.3941	$1,086.39	$1,086.40	$1,086.30