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 $183.66   7.702%   $197.8055   $197.81   $197.80   $197.80  
  Purchase #2 $63.86   7.505%   $68.6527   $68.65   $68.65   $68.70  
  Purchase #3 $51.60   8.410%   $55.9396   $55.94   $55.95   $55.90  
  Purchase #4 $236.59   10.412%   $261.2238   $261.22   $261.20   $261.20  
  Purchase #5 $56.62   10.715%   $62.6868   $62.69   $62.70   $62.70  
  Purchase #6 $90.79   4.858%   $95.2006   $95.20   $95.20   $95.20  
  Purchase #7 $239.97   11.854%   $268.416   $268.42   $268.40   $268.40  
  7 purchase totals = $923.09       $1,009.9250   $1,009.93   $1,009.90   $1,009.90