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	$30.72	12.429%	$34.5382	$34.54	$34.55	$34.50
Purchase #2	$91.69	4.294%	$95.6272	$95.63	$95.65	$95.60
Purchase #3	$82.25	6.419%	$87.5296	$87.53	$87.55	$87.50
Purchase #4	$107.94	4.697%	$113.0099	$113.01	$113.00	$113.00
Purchase #5	$227.25	12.767%	$256.263	$256.26	$256.25	$256.30
Purchase #6	$133.40	12.527%	$150.111	$150.11	$150.10	$150.10
Purchase #7	$106.94	11.340%	$119.067	$119.07	$119.05	$119.10
7 purchase totals =	$780.19		$856.1459	$856.15	$856.15	$856.10