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 $175.86   11.844%   $196.6889   $196.69   $196.70   $196.70  
  Purchase #2 $94.44   10.779%   $104.6197   $104.62   $104.60   $104.60  
  Purchase #3 $25.76   12.276%   $28.9223   $28.92   $28.90   $28.90  
  Purchase #4 $42.59   4.234%   $44.3933   $44.39   $44.40   $44.40  
  Purchase #5 $120.80   12.838%   $136.3083   $136.31   $136.30   $136.30  
  Purchase #6 $89.48   4.272%   $93.3026   $93.30   $93.30   $93.30  
  Purchase #7 $152.65   7.465%   $164.0453   $164.05   $164.05   $164.00  
  7 purchase totals = $701.58       $768.2804   $768.28   $768.25   $768.20