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 $243.90   7.416%   $261.9876   $261.99   $262.00   $262.00  
  Purchase #2 $43.98   4.399%   $45.9147   $45.91   $45.90   $45.90  
  Purchase #3 $134.67   8.791%   $146.5088   $146.51   $146.50   $146.50  
  Purchase #4 $91.58   12.661%   $103.1749   $103.17   $103.15   $103.20  
  Purchase #5 $241.26   7.675%   $259.7767   $259.78   $259.80   $259.80  
  Purchase #6 $240.92   12.661%   $271.4229   $271.42   $271.40   $271.40  
  Purchase #7 $24.62   11.472%   $27.4444   $27.44   $27.45   $27.40  
  7 purchase totals = $1,020.93       $1,116.2300   $1,116.22   $1,116.20   $1,116.20