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	$33.76	6.700%	$36.0219	$36.02	$36.00	$36.00
Purchase #2	$83.68	6.192%	$88.8615	$88.86	$88.85	$88.90
Purchase #3	$161.47	12.617%	$181.8427	$181.84	$181.85	$181.80
Purchase #4	$21.50	10.539%	$23.7659	$23.77	$23.75	$23.80
Purchase #5	$143.89	6.262%	$152.9004	$152.90	$152.90	$152.90
Purchase #6	$95.98	4.705%	$100.4959	$100.50	$100.50	$100.50
Purchase #7	$117.96	12.188%	$132.337	$132.34	$132.35	$132.30
7 purchase totals =	$658.24		$716.2253	$716.23	$716.20	$716.20