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 $84.91   12.139%   $95.2172   $95.22   $95.20   $95.20  
  Purchase #2 $233.76   13.414%   $265.1166   $265.12   $265.10   $265.10  
  Purchase #3 $35.83   7.518%   $38.5237   $38.52   $38.50   $38.50  
  Purchase #4 $104.58   4.311%   $109.0884   $109.09   $109.10   $109.10  
  Purchase #5 $218.90   5.570%   $231.0927   $231.09   $231.10   $231.10  
  Purchase #6 $89.74   6.434%   $95.5139   $95.51   $95.50   $95.50  
  Purchase #7 $47.88   3.720%   $49.6611   $49.66   $49.65   $49.70  
  7 purchase totals = $815.60       $884.2136   $884.21   $884.15   $884.20