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 $56.39   10.174%   $62.1271   $62.13   $62.15   $62.10  
  Purchase #2 $187.86   5.671%   $198.5135   $198.51   $198.50   $198.50  
  Purchase #3 $208.87   12.359%   $234.6842   $234.68   $234.70   $234.70  
  Purchase #4 $153.46   3.711%   $159.1549   $159.15   $159.15   $159.20  
  Purchase #5 $26.91   11.736%   $30.0682   $30.07   $30.05   $30.10  
  Purchase #6 $136.68   10.726%   $151.3403   $151.34   $151.35   $151.30  
  Purchase #7 $227.37   5.668%   $240.2573   $240.26   $240.25   $240.30  
  7 purchase totals = $997.54       $1,076.1455   $1,076.14   $1,076.15   $1,076.20