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 $88.87   7.414%   $95.4588   $95.46   $95.45   $95.50  
  Purchase #2 $100.65   3.232%   $103.903   $103.90   $103.90   $103.90  
  Purchase #3 $28.97   11.342%   $32.2558   $32.26   $32.25   $32.30  
  Purchase #4 $76.26   6.705%   $81.3732   $81.37   $81.35   $81.40  
  Purchase #5 $112.32   8.595%   $121.9739   $121.97   $121.95   $122.00  
  Purchase #6 $169.77   9.687%   $186.2156   $186.22   $186.20   $186.20  
  Purchase #7 $239.71   9.524%   $262.54   $262.54   $262.55   $262.50  
  7 purchase totals = $816.55       $883.7203   $883.72   $883.65   $883.80