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 $84.86   9.282%   $92.7367   $92.74   $92.75   $92.70  
  Purchase #2 $105.33   13.862%   $119.9308   $119.93   $119.95   $119.90  
  Purchase #3 $188.81   6.218%   $200.5502   $200.55   $200.55   $200.60  
  Purchase #4 $149.44   5.118%   $157.0883   $157.09   $157.10   $157.10  
  Purchase #5 $125.83   13.724%   $143.0989   $143.10   $143.10   $143.10  
  Purchase #6 $219.81   13.829%   $250.2075   $250.21   $250.20   $250.20  
  Purchase #7 $202.31   8.271%   $219.0431   $219.04   $219.05   $219.00  
  7 purchase totals = $1,076.39       $1,182.6555   $1,182.66   $1,182.70   $1,182.60