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 $53.85   10.767%   $59.648   $59.65   $59.65   $59.60  
  Purchase #2 $152.33   8.781%   $165.7061   $165.71   $165.70   $165.70  
  Purchase #3 $249.64   4.819%   $261.6702   $261.67   $261.65   $261.70  
  Purchase #4 $22.66   4.344%   $23.6444   $23.64   $23.65   $23.60  
  Purchase #5 $45.70   3.256%   $47.188   $47.19   $47.20   $47.20  
  Purchase #6 $133.72   5.744%   $141.4009   $141.40   $141.40   $141.40  
  Purchase #7 $5.92   6.323%   $6.2943   $6.29   $6.30   $6.30  
  7 purchase totals = $663.82       $705.5519   $705.55   $705.55   $705.50