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	$190.90	9.399%	$208.8427	$208.84	$208.85	$208.80
Purchase #2	$132.90	4.124%	$138.3808	$138.38	$138.40	$138.40
Purchase #3	$40.60	7.565%	$43.6714	$43.67	$43.65	$43.70
Purchase #4	$157.97	10.344%	$174.3104	$174.31	$174.30	$174.30
Purchase #5	$136.49	10.332%	$150.5921	$150.59	$150.60	$150.60
Purchase #6	$125.90	4.121%	$131.0883	$131.09	$131.10	$131.10
Purchase #7	$39.89	6.448%	$42.4621	$42.46	$42.45	$42.50
7 purchase totals =	$824.65		$889.3478	$889.34	$889.35	$889.40