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	$112.78	10.480%	$124.5993	$124.60	$124.60	$124.60
Purchase #2	$74.83	4.538%	$78.2258	$78.23	$78.25	$78.20
Purchase #3	$166.67	9.777%	$182.9653	$182.97	$182.95	$183.00
Purchase #4	$126.90	4.439%	$132.5331	$132.53	$132.55	$132.50
Purchase #5	$215.83	5.419%	$227.5258	$227.53	$227.55	$227.50
Purchase #6	$143.91	4.822%	$150.8493	$150.85	$150.85	$150.80
Purchase #7	$216.79	4.607%	$226.7775	$226.78	$226.80	$226.80
7 purchase totals =	$1,057.71		$1,123.4761	$1,123.49	$1,123.55	$1,123.40