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 $23.53   10.199%   $25.9298   $25.93   $25.95   $25.90  
  Purchase #2 $216.41   11.854%   $242.0632   $242.06   $242.05   $242.10  
  Purchase #3 $213.72   5.141%   $224.7073   $224.71   $224.70   $224.70  
  Purchase #4 $155.97   9.288%   $170.4565   $170.46   $170.45   $170.50  
  Purchase #5 $167.81   6.814%   $179.2446   $179.24   $179.25   $179.20  
  Purchase #6 $130.68   11.331%   $145.4874   $145.49   $145.50   $145.50  
  Purchase #7 $199.76   8.116%   $215.9725   $215.97   $215.95   $216.00  
  7 purchase totals = $1,107.88       $1,203.8613   $1,203.86   $1,203.85   $1,203.90