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	$37.57	8.695%	$40.8367	$40.84	$40.85	$40.80
Purchase #2	$196.81	6.182%	$208.9768	$208.98	$209.00	$209.00
Purchase #3	$14.70	5.584%	$15.5208	$15.52	$15.50	$15.50
Purchase #4	$97.49	8.254%	$105.5368	$105.54	$105.55	$105.50
Purchase #5	$90.36	13.776%	$102.808	$102.81	$102.80	$102.80
Purchase #6	$172.32	5.455%	$181.7201	$181.72	$181.70	$181.70
Purchase #7	$246.32	12.382%	$276.8193	$276.82	$276.80	$276.80
7 purchase totals =	$855.57		$932.2185	$932.23	$932.20	$932.10