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	$100.35	3.456%	$103.8181	$103.82	$103.80	$103.80
Purchase #2	$104.37	8.239%	$112.969	$112.97	$112.95	$113.00
Purchase #3	$118.80	11.477%	$132.4347	$132.43	$132.45	$132.40
Purchase #4	$85.63	8.624%	$93.0147	$93.01	$93.00	$93.00
Purchase #5	$92.60	6.447%	$98.5699	$98.57	$98.55	$98.60
Purchase #6	$219.56	6.545%	$233.9302	$233.93	$233.95	$233.90
Purchase #7	$172.34	11.328%	$191.8627	$191.86	$191.85	$191.90
7 purchase totals =	$893.65		$966.5993	$966.59	$966.55	$966.60