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 $23.46   11.143%   $26.0741   $26.07   $26.05   $26.10  
  Purchase #2 $165.94   5.670%   $175.3488   $175.35   $175.35   $175.30  
  Purchase #3 $30.97   4.585%   $32.39   $32.39   $32.40   $32.40  
  Purchase #4 $239.93   7.624%   $258.2223   $258.22   $258.20   $258.20  
  Purchase #5 $199.87   10.779%   $221.414   $221.41   $221.40   $221.40  
  Purchase #6 $235.48   6.489%   $250.7603   $250.76   $250.75   $250.80  
  Purchase #7 $136.60   6.737%   $145.8027   $145.80   $145.80   $145.80  
  7 purchase totals = $1,032.25       $1,110.0122   $1,110.00   $1,109.95   $1,110.00