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	$50.97	3.258%	$52.6306	$52.63	$52.65	$52.60
Purchase #2	$206.33	3.646%	$213.8528	$213.85	$213.85	$213.90
Purchase #3	$68.77	4.817%	$72.0827	$72.08	$72.10	$72.10
Purchase #4	$54.89	8.426%	$59.515	$59.52	$59.50	$59.50
Purchase #5	$154.45	12.723%	$174.1007	$174.10	$174.10	$174.10
Purchase #6	$125.52	11.149%	$139.5142	$139.51	$139.50	$139.50
Purchase #7	$182.94	11.346%	$203.6964	$203.70	$203.70	$203.70
7 purchase totals =	$843.87		$915.3924	$915.39	$915.40	$915.40