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 $232.67   5.384%   $245.197   $245.20   $245.20   $245.20  
  Purchase #2 $105.37   6.226%   $111.9303   $111.93   $111.95   $111.90  
  Purchase #3 $109.86   12.592%   $123.6936   $123.69   $123.70   $123.70  
  Purchase #4 $41.26   12.161%   $46.2776   $46.28   $46.30   $46.30  
  Purchase #5 $176.68   5.500%   $186.3974   $186.40   $186.40   $186.40  
  Purchase #6 $250.87   5.589%   $264.8911   $264.89   $264.90   $264.90  
  Purchase #7 $45.99   5.726%   $48.6234   $48.62   $48.60   $48.60  
  7 purchase totals = $962.70       $1,027.0104   $1,027.01   $1,027.05   $1,027.00