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	$210.84	5.704%	$222.8663	$222.87	$222.85	$222.90
Purchase #2	$132.63	7.735%	$142.8889	$142.89	$142.90	$142.90
Purchase #3	$240.67	7.398%	$258.4748	$258.47	$258.45	$258.50
Purchase #4	$90.97	10.767%	$100.7647	$100.76	$100.75	$100.80
Purchase #5	$241.36	3.289%	$249.2983	$249.30	$249.30	$249.30
Purchase #6	$162.47	3.716%	$168.5074	$168.51	$168.50	$168.50
Purchase #7	$174.67	5.285%	$183.9013	$183.90	$183.90	$183.90
7 purchase totals =	$1,253.61		$1,326.7017	$1,326.70	$1,326.65	$1,326.80