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	$88.65	13.680%	$100.7773	$100.78	$100.80	$100.80
Purchase #2	$23.68	3.262%	$24.4524	$24.45	$24.45	$24.50
Purchase #3	$30.45	4.777%	$31.9046	$31.90	$31.90	$31.90
Purchase #4	$240.85	6.476%	$256.4474	$256.45	$256.45	$256.40
Purchase #5	$198.41	6.575%	$211.4555	$211.46	$211.45	$211.50
Purchase #6	$203.99	5.573%	$215.3584	$215.36	$215.35	$215.40
Purchase #7	$83.50	13.113%	$94.4494	$94.45	$94.45	$94.40
7 purchase totals =	$869.53		$934.8450	$934.85	$934.85	$934.90