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	$57.81	11.554%	$64.4894	$64.49	$64.50	$64.50
Purchase #2	$122.52	7.372%	$131.5522	$131.55	$131.55	$131.60
Purchase #3	$156.78	3.697%	$162.5762	$162.58	$162.60	$162.60
Purchase #4	$150.70	5.815%	$159.4632	$159.46	$159.45	$159.50
Purchase #5	$103.97	11.591%	$116.0212	$116.02	$116.00	$116.00
Purchase #6	$46.40	11.311%	$51.6483	$51.65	$51.65	$51.60
Purchase #7	$233.60	13.775%	$265.7784	$265.78	$265.80	$265.80
7 purchase totals =	$871.78		$951.5289	$951.53	$951.55	$951.60