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	$207.43	3.575%	$214.8456	$214.85	$214.85	$214.80
Purchase #2	$196.81	11.725%	$219.886	$219.89	$219.90	$219.90
Purchase #3	$137.58	12.587%	$154.8972	$154.90	$154.90	$154.90
Purchase #4	$200.35	10.536%	$221.4589	$221.46	$221.45	$221.50
Purchase #5	$75.38	9.613%	$82.6263	$82.63	$82.65	$82.60
Purchase #6	$128.68	6.815%	$137.4495	$137.45	$137.45	$137.40
Purchase #7	$179.76	5.870%	$190.3119	$190.31	$190.30	$190.30
7 purchase totals =	$1,125.99		$1,221.4754	$1,221.49	$1,221.50	$1,221.40