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	$78.92	5.635%	$83.3671	$83.37	$83.35	$83.40
Purchase #2	$123.32	3.693%	$127.8742	$127.87	$127.85	$127.90
Purchase #3	$234.83	4.105%	$244.4698	$244.47	$244.45	$244.50
Purchase #4	$19.42	10.577%	$21.4741	$21.47	$21.45	$21.50
Purchase #5	$177.96	13.184%	$201.4222	$201.42	$201.40	$201.40
Purchase #6	$21.58	13.611%	$24.5173	$24.52	$24.50	$24.50
Purchase #7	$228.98	6.751%	$244.4384	$244.44	$244.45	$244.40
7 purchase totals =	$885.01		$947.5631	$947.56	$947.45	$947.60