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 $61.62   6.263%   $65.4793   $65.48   $65.50   $65.50  
  Purchase #2 $86.99   8.158%   $94.0866   $94.09   $94.10   $94.10  
  Purchase #3 $247.42   5.836%   $261.8594   $261.86   $261.85   $261.90  
  Purchase #4 $232.49   10.170%   $256.1342   $256.13   $256.15   $256.10  
  Purchase #5 $205.76   9.583%   $225.478   $225.48   $225.50   $225.50  
  Purchase #6 $149.53   12.307%   $167.9327   $167.93   $167.95   $167.90  
  Purchase #7 $28.99   4.830%   $30.3902   $30.39   $30.40   $30.40  
  7 purchase totals = $1,012.80       $1,101.3604   $1,101.36   $1,101.45   $1,101.40