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 $61.49   6.814%   $65.6799   $65.68   $65.70   $65.70  
  Purchase #2 $225.58   5.111%   $237.1094   $237.11   $237.10   $237.10  
  Purchase #3 $8.32   3.156%   $8.5826   $8.58   $8.60   $8.60  
  Purchase #4 $217.28   6.814%   $232.0855   $232.09   $232.10   $232.10  
  Purchase #5 $209.29   8.528%   $227.1383   $227.14   $227.15   $227.10  
  Purchase #6 $43.76   4.687%   $45.811   $45.81   $45.80   $45.80  
  Purchase #7 $93.90   4.328%   $97.964   $97.96   $97.95   $98.00  
  7 purchase totals = $859.62       $914.3707   $914.37   $914.40   $914.40