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 $197.32   5.411%   $207.997   $208.00   $208.00   $208.00  
  Purchase #2 $240.88   5.797%   $254.8438   $254.84   $254.85   $254.80  
  Purchase #3 $134.53   10.790%   $149.0458   $149.05   $149.05   $149.00  
  Purchase #4 $7.82   9.456%   $8.5595   $8.56   $8.55   $8.60  
  Purchase #5 $161.90   8.587%   $175.8024   $175.80   $175.80   $175.80  
  Purchase #6 $42.82   8.792%   $46.5847   $46.58   $46.60   $46.60  
  Purchase #7 $170.46   3.724%   $176.8079   $176.81   $176.80   $176.80  
  7 purchase totals = $955.73       $1,019.6411   $1,019.64   $1,019.65   $1,019.60