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 $113.67   11.462%   $126.6989   $126.70   $126.70   $126.70  
  Purchase #2 $17.75   8.244%   $19.2133   $19.21   $19.20   $19.20  
  Purchase #3 $54.62   4.259%   $56.9463   $56.95   $56.95   $56.90  
  Purchase #4 $18.74   3.850%   $19.4615   $19.46   $19.45   $19.50  
  Purchase #5 $201.95   3.569%   $209.1576   $209.16   $209.15   $209.20  
  Purchase #6 $236.63   13.501%   $268.5774   $268.58   $268.60   $268.60  
  Purchase #7 $243.91   9.693%   $267.5522   $267.55   $267.55   $267.60  
  7 purchase totals = $887.27       $967.6072   $967.61   $967.60   $967.70