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 $57.32   8.499%   $62.1916   $62.19   $62.20   $62.20  
  Purchase #2 $45.89   5.354%   $48.347   $48.35   $48.35   $48.30  
  Purchase #3 $223.45   4.568%   $233.6572   $233.66   $233.65   $233.70  
  Purchase #4 $33.81   5.836%   $35.7832   $35.78   $35.80   $35.80  
  Purchase #5 $235.46   4.296%   $245.5754   $245.58   $245.60   $245.60  
  Purchase #6 $212.51   3.787%   $220.5578   $220.56   $220.55   $220.60  
  Purchase #7 $20.37   10.410%   $22.4905   $22.49   $22.50   $22.50  
  7 purchase totals = $828.81       $868.6027   $868.61   $868.65   $868.70