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 $24.57   7.165%   $26.3304   $26.33   $26.35   $26.30  
  Purchase #2 $186.52   5.259%   $196.3291   $196.33   $196.35   $196.30  
  Purchase #3 $162.75   7.484%   $174.9302   $174.93   $174.95   $174.90  
  Purchase #4 $217.56   3.568%   $225.3225   $225.32   $225.30   $225.30  
  Purchase #5 $157.63   10.639%   $174.4003   $174.40   $174.40   $174.40  
  Purchase #6 $243.42   7.112%   $260.732   $260.73   $260.75   $260.70  
  Purchase #7 $50.85   10.398%   $56.1374   $56.14   $56.15   $56.10  
  7 purchase totals = $1,043.30       $1,114.1819   $1,114.18   $1,114.25   $1,114.00