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	$69.62	9.777%	$76.4267	$76.43	$76.45	$76.40
Purchase #2	$62.98	9.229%	$68.7924	$68.79	$68.80	$68.80
Purchase #3	$201.75	8.252%	$218.3984	$218.40	$218.40	$218.40
Purchase #4	$86.35	3.119%	$89.0433	$89.04	$89.05	$89.00
Purchase #5	$64.42	3.867%	$66.9111	$66.91	$66.90	$66.90
Purchase #6	$71.59	9.580%	$78.4483	$78.45	$78.45	$78.40
Purchase #7	$22.91	11.189%	$25.4734	$25.47	$25.45	$25.50
7 purchase totals =	$579.62		$623.4936	$623.49	$623.50	$623.40