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 $22.69   8.691%   $24.662   $24.66   $24.65   $24.70  
  Purchase #2 $108.93   13.521%   $123.6584   $123.66   $123.65   $123.70  
  Purchase #3 $150.52   8.682%   $163.5881   $163.59   $163.60   $163.60  
  Purchase #4 $183.98   13.366%   $208.5708   $208.57   $208.55   $208.60  
  Purchase #5 $163.43   4.444%   $170.6928   $170.69   $170.70   $170.70  
  Purchase #6 $192.70   8.546%   $209.1681   $209.17   $209.15   $209.20  
  Purchase #7 $43.49   7.281%   $46.6565   $46.66   $46.65   $46.70  
  7 purchase totals = $865.74       $946.9967   $947.00   $946.95   $947.20