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	$48.69	13.553%	$55.289	$55.29	$55.30	$55.30
Purchase #2	$80.60	8.637%	$87.5614	$87.56	$87.55	$87.60
Purchase #3	$194.59	8.700%	$211.5193	$211.52	$211.50	$211.50
Purchase #4	$182.62	4.758%	$191.3091	$191.31	$191.30	$191.30
Purchase #5	$205.37	7.357%	$220.4791	$220.48	$220.50	$220.50
Purchase #6	$205.47	9.439%	$224.8643	$224.86	$224.85	$224.90
Purchase #7	$61.53	11.319%	$68.4946	$68.49	$68.50	$68.50
7 purchase totals =	$978.87		$1,059.5168	$1,059.51	$1,059.50	$1,059.60