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 $91.66   4.834%   $96.0908   $96.09   $96.10   $96.10  
  Purchase #2 $222.95   13.445%   $252.9256   $252.93   $252.95   $252.90  
  Purchase #3 $180.66   7.214%   $193.6928   $193.69   $193.70   $193.70  
  Purchase #4 $202.61   7.382%   $217.5667   $217.57   $217.55   $217.60  
  Purchase #5 $147.68   7.414%   $158.629   $158.63   $158.65   $158.60  
  Purchase #6 $105.97   7.557%   $113.9782   $113.98   $114.00   $114.00  
  Purchase #7 $189.47   5.649%   $200.1732   $200.17   $200.15   $200.20  
  7 purchase totals = $1,141.00       $1,233.0563   $1,233.06   $1,233.10   $1,233.10