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	$32.38	4.338%	$33.7846	$33.78	$33.80	$33.80
Purchase #2	$224.46	13.409%	$254.5578	$254.56	$254.55	$254.60
Purchase #3	$207.42	9.806%	$227.7596	$227.76	$227.75	$227.80
Purchase #4	$79.83	8.394%	$86.5309	$86.53	$86.55	$86.50
Purchase #5	$176.56	11.293%	$196.4989	$196.50	$196.50	$196.50
Purchase #6	$131.29	3.725%	$136.1806	$136.18	$136.20	$136.20
Purchase #7	$95.87	12.795%	$108.1366	$108.14	$108.15	$108.10
7 purchase totals =	$947.81		$1,043.4490	$1,043.45	$1,043.50	$1,043.50