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 $218.69   8.809%   $237.9544   $237.95   $237.95   $238.00  
  Purchase #2 $103.25   13.806%   $117.5047   $117.50   $117.50   $117.50  
  Purchase #3 $66.85   5.273%   $70.375   $70.38   $70.40   $70.40  
  Purchase #4 $217.85   9.243%   $237.9859   $237.99   $238.00   $238.00  
  Purchase #5 $41.46   4.811%   $43.4546   $43.45   $43.45   $43.50  
  Purchase #6 $11.42   4.856%   $11.9746   $11.97   $11.95   $12.00  
  Purchase #7 $33.42   6.672%   $35.6498   $35.65   $35.65   $35.60  
  7 purchase totals = $692.94       $754.8990   $754.89   $754.90   $755.00