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	$202.96	5.664%	$214.4557	$214.46	$214.45	$214.50
Purchase #2	$124.80	9.386%	$136.5137	$136.51	$136.50	$136.50
Purchase #3	$9.99	4.360%	$10.4256	$10.43	$10.45	$10.40
Purchase #4	$115.61	9.382%	$126.4565	$126.46	$126.45	$126.50
Purchase #5	$34.97	8.700%	$38.0124	$38.01	$38.00	$38.00
Purchase #6	$71.78	9.387%	$78.518	$78.52	$78.50	$78.50
Purchase #7	$130.47	9.438%	$142.7838	$142.78	$142.80	$142.80
7 purchase totals =	$690.58		$747.1657	$747.17	$747.15	$747.20