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 $58.69   5.698%   $62.0342   $62.03   $62.05   $62.00  
  Purchase #2 $168.98   8.546%   $183.421   $183.42   $183.40   $183.40  
  Purchase #3 $136.87   13.197%   $154.9327   $154.93   $154.95   $154.90  
  Purchase #4 $50.26   12.345%   $56.4646   $56.46   $56.45   $56.50  
  Purchase #5 $180.91   8.463%   $196.2204   $196.22   $196.20   $196.20  
  Purchase #6 $235.84   9.623%   $258.5349   $258.53   $258.55   $258.50  
  Purchase #7 $150.88   8.696%   $164.0005   $164.00   $164.00   $164.00  
  7 purchase totals = $982.43       $1,075.6083   $1,075.59   $1,075.60   $1,075.50