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	$131.71	7.340%	$141.3775	$141.38	$141.40	$141.40
Purchase #2	$144.76	4.665%	$151.5131	$151.51	$151.50	$151.50
Purchase #3	$118.42	13.630%	$134.5606	$134.56	$134.55	$134.60
Purchase #4	$30.53	13.730%	$34.7218	$34.72	$34.70	$34.70
Purchase #5	$132.48	3.334%	$136.8969	$136.90	$136.90	$136.90
Purchase #6	$160.41	8.530%	$174.093	$174.09	$174.10	$174.10
Purchase #7	$80.94	11.566%	$90.3015	$90.30	$90.30	$90.30
7 purchase totals =	$799.25		$863.4644	$863.46	$863.45	$863.50