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 $189.32   6.149%   $200.9613   $200.96   $200.95   $201.00  
  Purchase #2 $207.54   8.653%   $225.4984   $225.50   $225.50   $225.50  
  Purchase #3 $215.71   5.755%   $228.1241   $228.12   $228.10   $228.10  
  Purchase #4 $210.96   8.593%   $229.0878   $229.09   $229.10   $229.10  
  Purchase #5 $85.93   8.471%   $93.2091   $93.21   $93.20   $93.20  
  Purchase #6 $245.76   6.607%   $261.9974   $262.00   $262.00   $262.00  
  Purchase #7 $135.60   6.309%   $144.155   $144.16   $144.15   $144.20  
  7 purchase totals = $1,290.82       $1,383.0331   $1,383.04   $1,383.00   $1,383.10