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	$58.94	11.587%	$65.7694	$65.77	$65.75	$65.80
Purchase #2	$153.51	6.136%	$162.9294	$162.93	$162.95	$162.90
Purchase #3	$183.97	11.614%	$205.3363	$205.34	$205.35	$205.30
Purchase #4	$178.75	11.662%	$199.5958	$199.60	$199.60	$199.60
Purchase #5	$43.49	7.674%	$46.8274	$46.83	$46.85	$46.80
Purchase #6	$20.86	3.723%	$21.6366	$21.64	$21.65	$21.60
Purchase #7	$245.89	4.330%	$256.537	$256.54	$256.55	$256.50
7 purchase totals =	$885.41		$958.6319	$958.65	$958.70	$958.50