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	$38.85	10.262%	$42.8368	$42.84	$42.85	$42.80
Purchase #2	$111.34	11.178%	$123.7856	$123.79	$123.80	$123.80
Purchase #3	$108.84	8.776%	$118.3918	$118.39	$118.40	$118.40
Purchase #4	$61.94	8.223%	$67.0333	$67.03	$67.05	$67.00
Purchase #5	$239.67	10.789%	$265.528	$265.53	$265.55	$265.50
Purchase #6	$198.47	11.119%	$220.5379	$220.54	$220.55	$220.50
Purchase #7	$204.84	9.788%	$224.8897	$224.89	$224.90	$224.90
7 purchase totals =	$963.95		$1,063.0031	$1,063.01	$1,063.10	$1,062.90