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	$94.92	9.480%	$103.9184	$103.92	$103.90	$103.90
Purchase #2	$140.90	8.633%	$153.0639	$153.06	$153.05	$153.10
Purchase #3	$213.81	5.430%	$225.4199	$225.42	$225.40	$225.40
Purchase #4	$209.78	11.178%	$233.2292	$233.23	$233.25	$233.20
Purchase #5	$225.64	3.482%	$233.4968	$233.50	$233.50	$233.50
Purchase #6	$156.38	10.478%	$172.7655	$172.77	$172.75	$172.80
Purchase #7	$186.80	12.743%	$210.6039	$210.60	$210.60	$210.60
7 purchase totals =	$1,228.23		$1,332.4976	$1,332.50	$1,332.45	$1,332.50