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	$157.75	9.429%	$172.6242	$172.62	$172.60	$172.60
Purchase #2	$115.51	7.768%	$124.4828	$124.48	$124.50	$124.50
Purchase #3	$44.46	7.706%	$47.8861	$47.89	$47.90	$47.90
Purchase #4	$170.98	6.217%	$181.6098	$181.61	$181.60	$181.60
Purchase #5	$103.33	9.300%	$112.9397	$112.94	$112.95	$112.90
Purchase #6	$29.48	7.325%	$31.6394	$31.64	$31.65	$31.60
Purchase #7	$109.29	6.221%	$116.0889	$116.09	$116.10	$116.10
7 purchase totals =	$730.80		$787.2709	$787.27	$787.30	$787.20