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	$128.39	4.582%	$134.2728	$134.27	$134.25	$134.30
Purchase #2	$43.34	12.131%	$48.5976	$48.60	$48.60	$48.60
Purchase #3	$195.45	4.861%	$204.9508	$204.95	$204.95	$205.00
Purchase #4	$139.86	12.683%	$157.5984	$157.60	$157.60	$157.60
Purchase #5	$90.82	10.761%	$100.5931	$100.59	$100.60	$100.60
Purchase #6	$97.64	8.661%	$106.0966	$106.10	$106.10	$106.10
Purchase #7	$57.60	12.280%	$64.6733	$64.67	$64.65	$64.70
7 purchase totals =	$753.10		$816.7826	$816.78	$816.75	$816.90