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 $119.34   5.553%   $125.967   $125.97   $125.95   $126.00  
  Purchase #2 $7.60   12.357%   $8.5391   $8.54   $8.55   $8.50  
  Purchase #3 $234.92   3.270%   $242.6019   $242.60   $242.60   $242.60  
  Purchase #4 $22.59   5.188%   $23.762   $23.76   $23.75   $23.80  
  Purchase #5 $232.83   8.815%   $253.354   $253.35   $253.35   $253.40  
  Purchase #6 $101.29   3.808%   $105.1471   $105.15   $105.15   $105.10  
  Purchase #7 $240.72   9.822%   $264.3635   $264.36   $264.35   $264.40  
  7 purchase totals = $959.29       $1,023.7346   $1,023.73   $1,023.70   $1,023.80