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 $195.94   6.157%   $208.004   $208.00   $208.00   $208.00  
  Purchase #2 $14.46   3.335%   $14.9422   $14.94   $14.95   $14.90  
  Purchase #3 $45.44   3.644%   $47.0958   $47.10   $47.10   $47.10  
  Purchase #4 $134.58   6.536%   $143.3761   $143.38   $143.40   $143.40  
  Purchase #5 $94.96   10.252%   $104.6953   $104.70   $104.70   $104.70  
  Purchase #6 $175.77   4.426%   $183.5496   $183.55   $183.55   $183.50  
  Purchase #7 $229.43   12.227%   $257.4824   $257.48   $257.50   $257.50  
  7 purchase totals = $890.58       $959.1454   $959.15   $959.20   $959.10