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 $61.53   6.534%   $65.5504   $65.55   $65.55   $65.60  
  Purchase #2 $112.38   3.265%   $116.0492   $116.05   $116.05   $116.00  
  Purchase #3 $170.35   9.215%   $186.0478   $186.05   $186.05   $186.00  
  Purchase #4 $111.64   12.297%   $125.3684   $125.37   $125.35   $125.40  
  Purchase #5 $238.61   9.752%   $261.8792   $261.88   $261.90   $261.90  
  Purchase #6 $114.29   12.775%   $128.8905   $128.89   $128.90   $128.90  
  Purchase #7 $236.80   5.728%   $250.3639   $250.36   $250.35   $250.40  
  7 purchase totals = $1,045.60       $1,134.1494   $1,134.15   $1,134.15   $1,134.20