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 $68.33   11.184%   $75.972   $75.97   $75.95   $76.00  
  Purchase #2 $134.88   4.623%   $141.1155   $141.12   $141.10   $141.10  
  Purchase #3 $78.46   9.202%   $85.6799   $85.68   $85.70   $85.70  
  Purchase #4 $191.93   7.576%   $206.4706   $206.47   $206.45   $206.50  
  Purchase #5 $184.83   8.651%   $200.8196   $200.82   $200.80   $200.80  
  Purchase #6 $9.74   4.141%   $10.1433   $10.14   $10.15   $10.10  
  Purchase #7 $86.78   4.737%   $90.8908   $90.89   $90.90   $90.90  
  7 purchase totals = $754.95       $811.0917   $811.09   $811.05   $811.10