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	$83.34	7.528%	$89.6138	$89.61	$89.60	$89.60
Purchase #2	$44.65	4.851%	$46.816	$46.82	$46.80	$46.80
Purchase #3	$29.44	10.360%	$32.49	$32.49	$32.50	$32.50
Purchase #4	$200.25	6.177%	$212.6194	$212.62	$212.60	$212.60
Purchase #5	$130.97	10.584%	$144.8319	$144.83	$144.85	$144.80
Purchase #6	$215.49	8.457%	$233.714	$233.71	$233.70	$233.70
Purchase #7	$177.27	12.479%	$199.3915	$199.39	$199.40	$199.40
7 purchase totals =	$881.41		$959.4766	$959.47	$959.45	$959.40