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 $61.61   10.676%   $68.1875   $68.19   $68.20   $68.20  
  Purchase #2 $96.67   8.267%   $104.6617   $104.66   $104.65   $104.70  
  Purchase #3 $95.33   13.509%   $108.2081   $108.21   $108.20   $108.20  
  Purchase #4 $177.70   5.871%   $188.1328   $188.13   $188.15   $188.10  
  Purchase #5 $217.76   4.795%   $228.2016   $228.20   $228.20   $228.20  
  Purchase #6 $187.68   9.583%   $205.6654   $205.67   $205.65   $205.70  
  Purchase #7 $237.49   5.339%   $250.1696   $250.17   $250.15   $250.20  
  7 purchase totals = $1,074.24       $1,153.2267   $1,153.23   $1,153.20   $1,153.30