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 $239.46   9.618%   $262.4913   $262.49   $262.50   $262.50  
  Purchase #2 $84.62   11.685%   $94.5078   $94.51   $94.50   $94.50  
  Purchase #3 $33.90   13.271%   $38.3989   $38.40   $38.40   $38.40  
  Purchase #4 $76.80   13.707%   $87.327   $87.33   $87.35   $87.30  
  Purchase #5 $125.44   5.241%   $132.0143   $132.01   $132.00   $132.00  
  Purchase #6 $196.90   9.280%   $215.1723   $215.17   $215.15   $215.20  
  Purchase #7 $220.62   7.872%   $237.9872   $237.99   $238.00   $238.00  
  7 purchase totals = $977.74       $1,067.8988   $1,067.90   $1,067.90   $1,067.90