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 $118.87   5.681%   $125.623   $125.62   $125.60   $125.60  
  Purchase #2 $206.70   11.710%   $230.9046   $230.90   $230.90   $230.90  
  Purchase #3 $51.92   8.127%   $56.1395   $56.14   $56.15   $56.10  
  Purchase #4 $248.45   5.359%   $261.7644   $261.76   $261.75   $261.80  
  Purchase #5 $84.54   8.753%   $91.9398   $91.94   $91.95   $91.90  
  Purchase #6 $191.96   9.462%   $210.1233   $210.12   $210.10   $210.10  
  Purchase #7 $120.76   13.302%   $136.8235   $136.82   $136.80   $136.80  
  7 purchase totals = $1,023.20       $1,113.3181   $1,113.30   $1,113.25   $1,113.20