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 $208.70   8.494%   $226.427   $226.43   $226.45   $226.40  
  Purchase #2 $200.78   13.423%   $227.7307   $227.73   $227.75   $227.70  
  Purchase #3 $125.60   7.527%   $135.0539   $135.05   $135.05   $135.10  
  Purchase #4 $173.63   5.386%   $182.9817   $182.98   $183.00   $183.00  
  Purchase #5 $47.35   3.544%   $49.0281   $49.03   $49.05   $49.00  
  Purchase #6 $236.52   4.622%   $247.452   $247.45   $247.45   $247.50  
  Purchase #7 $33.69   5.315%   $35.4806   $35.48   $35.50   $35.50  
  7 purchase totals = $1,026.27       $1,104.1540   $1,104.15   $1,104.25   $1,104.20