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 $86.59   13.491%   $98.2719   $98.27   $98.25   $98.30  
  Purchase #2 $44.54   3.156%   $45.9457   $45.95   $45.95   $45.90  
  Purchase #3 $24.98   4.125%   $26.0104   $26.01   $26.00   $26.00  
  Purchase #4 $37.96   9.304%   $41.4918   $41.49   $41.50   $41.50  
  Purchase #5 $201.92   10.153%   $222.4209   $222.42   $222.40   $222.40  
  Purchase #6 $139.50   4.694%   $146.0481   $146.05   $146.05   $146.00  
  Purchase #7 $161.65   8.685%   $175.6893   $175.69   $175.70   $175.70  
  7 purchase totals = $697.14       $755.8781   $755.88   $755.85   $755.80