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	$178.94	5.590%	$188.9427	$188.94	$188.95	$188.90
Purchase #2	$153.39	9.212%	$167.5203	$167.52	$167.50	$167.50
Purchase #3	$246.26	6.582%	$262.4688	$262.47	$262.45	$262.50
Purchase #4	$37.62	7.305%	$40.3681	$40.37	$40.35	$40.40
Purchase #5	$43.61	8.440%	$47.2907	$47.29	$47.30	$47.30
Purchase #6	$190.69	11.423%	$212.4725	$212.47	$212.45	$212.50
Purchase #7	$132.54	3.709%	$137.4559	$137.46	$137.45	$137.50
7 purchase totals =	$983.05		$1,056.5190	$1,056.52	$1,056.45	$1,056.60