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	$97.25	8.105%	$105.1321	$105.13	$105.15	$105.10
Purchase #2	$124.38	6.118%	$131.9896	$131.99	$132.00	$132.00
Purchase #3	$81.92	8.839%	$89.1609	$89.16	$89.15	$89.20
Purchase #4	$30.76	6.166%	$32.6567	$32.66	$32.65	$32.70
Purchase #5	$187.80	4.723%	$196.6698	$196.67	$196.65	$196.70
Purchase #6	$130.80	4.685%	$136.928	$136.93	$136.95	$136.90
Purchase #7	$89.53	5.832%	$94.7514	$94.75	$94.75	$94.80
7 purchase totals =	$742.44		$787.2885	$787.29	$787.30	$787.40