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	$30.37	8.156%	$32.847	$32.85	$32.85	$32.80
Purchase #2	$140.47	9.636%	$154.0057	$154.01	$154.00	$154.00
Purchase #3	$248.42	5.601%	$262.334	$262.33	$262.35	$262.30
Purchase #4	$9.78	3.425%	$10.115	$10.12	$10.10	$10.10
Purchase #5	$36.93	13.330%	$41.8528	$41.85	$41.85	$41.90
Purchase #6	$29.97	12.310%	$33.6593	$33.66	$33.65	$33.70
Purchase #7	$154.38	7.393%	$165.7933	$165.79	$165.80	$165.80
7 purchase totals =	$650.32		$700.6071	$700.61	$700.60	$700.60