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	$168.74	13.734%	$191.9148	$191.91	$191.90	$191.90
Purchase #2	$19.51	10.290%	$21.5176	$21.52	$21.50	$21.50
Purchase #3	$232.72	4.193%	$242.4779	$242.48	$242.50	$242.50
Purchase #4	$131.93	12.822%	$148.8461	$148.85	$148.85	$148.80
Purchase #5	$71.63	9.826%	$78.6684	$78.67	$78.65	$78.70
Purchase #6	$169.43	9.124%	$184.8888	$184.89	$184.90	$184.90
Purchase #7	$41.75	7.114%	$44.7201	$44.72	$44.70	$44.70
7 purchase totals =	$835.71		$913.0337	$913.04	$913.00	$913.00