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	$138.65	12.868%	$156.4915	$156.49	$156.50	$156.50
Purchase #2	$25.92	5.221%	$27.2733	$27.27	$27.25	$27.30
Purchase #3	$13.68	5.481%	$14.4298	$14.43	$14.45	$14.40
Purchase #4	$41.89	9.477%	$45.8599	$45.86	$45.85	$45.90
Purchase #5	$70.77	3.292%	$73.0997	$73.10	$73.10	$73.10
Purchase #6	$6.49	6.134%	$6.8881	$6.89	$6.90	$6.90
Purchase #7	$108.50	11.139%	$120.5858	$120.59	$120.60	$120.60
7 purchase totals =	$405.90		$444.6281	$444.63	$444.65	$444.70