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	$238.55	8.455%	$258.7194	$258.72	$258.70	$258.70
Purchase #2	$205.73	11.102%	$228.5701	$228.57	$228.55	$228.60
Purchase #3	$103.65	13.463%	$117.6044	$117.60	$117.60	$117.60
Purchase #4	$50.57	7.699%	$54.4634	$54.46	$54.45	$54.50
Purchase #5	$71.89	12.531%	$80.8985	$80.90	$80.90	$80.90
Purchase #6	$166.39	9.339%	$181.9292	$181.93	$181.95	$181.90
Purchase #7	$110.91	12.271%	$124.5198	$124.52	$124.50	$124.50
7 purchase totals =	$947.69		$1,046.7048	$1,046.70	$1,046.65	$1,046.70