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 $59.58   10.696%   $65.9527   $65.95   $65.95   $66.00  
  Purchase #2 $106.51   13.472%   $120.859   $120.86   $120.85   $120.90  
  Purchase #3 $146.93   6.296%   $156.1807   $156.18   $156.20   $156.20  
  Purchase #4 $232.58   5.724%   $245.8929   $245.89   $245.90   $245.90  
  Purchase #5 $237.83   10.235%   $262.1719   $262.17   $262.15   $262.20  
  Purchase #6 $124.57   9.336%   $136.1999   $136.20   $136.20   $136.20  
  Purchase #7 $122.33   10.782%   $135.5196   $135.52   $135.50   $135.50  
  7 purchase totals = $1,030.33       $1,122.7767   $1,122.77   $1,122.75   $1,122.90