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 $167.50   4.207%   $174.5467   $174.55   $174.55   $174.50  
  Purchase #2 $238.37   8.153%   $257.8043   $257.80   $257.80   $257.80  
  Purchase #3 $106.47   6.213%   $113.085   $113.09   $113.10   $113.10  
  Purchase #4 $211.80   12.125%   $237.4808   $237.48   $237.50   $237.50  
  Purchase #5 $23.68   5.186%   $24.908   $24.91   $24.90   $24.90  
  Purchase #6 $86.71   6.165%   $92.0557   $92.06   $92.05   $92.10  
  Purchase #7 $61.53   8.765%   $66.9231   $66.92   $66.90   $66.90  
  7 purchase totals = $896.06       $966.8036   $966.81   $966.80   $966.80