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	$195.57	10.388%	$215.8858	$215.89	$215.90	$215.90
Purchase #2	$60.70	9.792%	$66.6437	$66.64	$66.65	$66.60
Purchase #3	$99.37	4.582%	$103.9231	$103.92	$103.90	$103.90
Purchase #4	$179.61	11.869%	$200.9279	$200.93	$200.95	$200.90
Purchase #5	$21.43	12.235%	$24.052	$24.05	$24.05	$24.10
Purchase #6	$201.39	9.672%	$220.8684	$220.87	$220.85	$220.90
Purchase #7	$44.96	12.184%	$50.4379	$50.44	$50.45	$50.40
7 purchase totals =	$803.03		$882.7388	$882.74	$882.75	$882.70