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 $58.62   8.471%   $63.5857   $63.59   $63.60   $63.60  
  Purchase #2 $234.96   4.780%   $246.1911   $246.19   $246.20   $246.20  
  Purchase #3 $76.92   6.533%   $81.9452   $81.95   $81.95   $81.90  
  Purchase #4 $148.86   8.262%   $161.1588   $161.16   $161.15   $161.20  
  Purchase #5 $207.41   4.232%   $216.1876   $216.19   $216.20   $216.20  
  Purchase #6 $90.72   12.820%   $102.3503   $102.35   $102.35   $102.40  
  Purchase #7 $225.69   4.453%   $235.74   $235.74   $235.75   $235.70  
  7 purchase totals = $1,043.18       $1,107.1587   $1,107.17   $1,107.20   $1,107.20