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 $56.31   11.719%   $62.909   $62.91   $62.90   $62.90  
  Purchase #2 $192.41   5.247%   $202.5058   $202.51   $202.50   $202.50  
  Purchase #3 $27.47   10.818%   $30.4417   $30.44   $30.45   $30.40  
  Purchase #4 $106.91   11.540%   $119.2474   $119.25   $119.25   $119.20  
  Purchase #5 $250.72   13.447%   $284.4343   $284.43   $284.45   $284.40  
  Purchase #6 $24.45   11.280%   $27.208   $27.21   $27.20   $27.20  
  Purchase #7 $33.29   7.489%   $35.7831   $35.78   $35.80   $35.80  
  7 purchase totals = $691.56       $762.5293   $762.53   $762.55   $762.40