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 $44.38   8.290%   $48.0591   $48.06   $48.05   $48.10  
  Purchase #2 $201.89   12.656%   $227.4412   $227.44   $227.45   $227.40  
  Purchase #3 $187.99   6.704%   $200.5928   $200.59   $200.60   $200.60  
  Purchase #4 $165.68   10.271%   $182.697   $182.70   $182.70   $182.70  
  Purchase #5 $23.48   8.267%   $25.4211   $25.42   $25.40   $25.40  
  Purchase #6 $196.59   6.647%   $209.6573   $209.66   $209.65   $209.70  
  Purchase #7 $98.91   3.242%   $102.1167   $102.12   $102.10   $102.10  
  7 purchase totals = $918.92       $995.9852   $995.99   $995.95   $996.00