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	$102.51	13.625%	$116.477	$116.48	$116.50	$116.50
Purchase #2	$242.37	6.232%	$257.4745	$257.47	$257.45	$257.50
Purchase #3	$76.51	7.300%	$82.0952	$82.10	$82.10	$82.10
Purchase #4	$44.99	5.682%	$47.5463	$47.55	$47.55	$47.50
Purchase #5	$169.27	5.717%	$178.9472	$178.95	$178.95	$178.90
Purchase #6	$221.59	5.357%	$233.4606	$233.46	$233.45	$233.50
Purchase #7	$128.71	13.717%	$146.3652	$146.37	$146.35	$146.40
7 purchase totals =	$985.95		$1,062.3660	$1,062.38	$1,062.35	$1,062.40