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	$37.47	10.826%	$41.5265	$41.53	$41.55	$41.50
Purchase #2	$117.62	11.274%	$130.8805	$130.88	$130.90	$130.90
Purchase #3	$97.92	5.702%	$103.5034	$103.50	$103.50	$103.50
Purchase #4	$14.30	10.547%	$15.8082	$15.81	$15.80	$15.80
Purchase #5	$217.93	8.497%	$236.4475	$236.45	$236.45	$236.40
Purchase #6	$94.53	5.594%	$99.818	$99.82	$99.80	$99.80
Purchase #7	$135.71	4.238%	$141.4614	$141.46	$141.45	$141.50
7 purchase totals =	$715.48		$769.4455	$769.45	$769.45	$769.40