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 $56.27   4.785%   $58.9625   $58.96   $58.95   $59.00  
  Purchase #2 $232.68   12.787%   $262.4328   $262.43   $262.45   $262.40  
  Purchase #3 $191.30   5.124%   $201.1022   $201.10   $201.10   $201.10  
  Purchase #4 $164.43   13.655%   $186.8829   $186.88   $186.90   $186.90  
  Purchase #5 $40.45   3.134%   $41.7177   $41.72   $41.70   $41.70  
  Purchase #6 $245.62   6.667%   $261.9955   $262.00   $262.00   $262.00  
  Purchase #7 $10.50   4.339%   $10.9556   $10.96   $10.95   $11.00  
  7 purchase totals = $941.25       $1,024.0492   $1,024.05   $1,024.05   $1,024.10