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	$217.25	11.391%	$241.9969	$242.00	$242.00	$242.00
Purchase #2	$108.88	3.409%	$112.5917	$112.59	$112.60	$112.60
Purchase #3	$230.60	13.873%	$262.5911	$262.59	$262.60	$262.60
Purchase #4	$162.93	4.192%	$169.76	$169.76	$169.75	$169.80
Purchase #5	$14.68	10.528%	$16.2255	$16.23	$16.25	$16.20
Purchase #6	$172.76	7.171%	$185.1486	$185.15	$185.15	$185.10
Purchase #7	$40.37	5.517%	$42.5972	$42.60	$42.60	$42.60
7 purchase totals =	$947.47		$1,030.9110	$1,030.92	$1,030.95	$1,030.90