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	$156.51	11.423%	$174.3881	$174.39	$174.40	$174.40
Purchase #2	$233.68	11.410%	$260.3429	$260.34	$260.35	$260.30
Purchase #3	$85.57	5.757%	$90.4963	$90.50	$90.50	$90.50
Purchase #4	$39.28	10.691%	$43.4794	$43.48	$43.50	$43.50
Purchase #5	$199.55	7.529%	$214.5741	$214.57	$214.55	$214.60
Purchase #6	$211.95	3.838%	$220.0846	$220.08	$220.10	$220.10
Purchase #7	$118.35	4.425%	$123.587	$123.59	$123.60	$123.60
7 purchase totals =	$1,044.89		$1,126.9524	$1,126.95	$1,127.00	$1,127.00