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 $12.55   13.469%   $14.2404   $14.24   $14.25   $14.20  
  Purchase #2 $182.83   5.813%   $193.4579   $193.46   $193.45   $193.50  
  Purchase #3 $187.36   5.554%   $197.766   $197.77   $197.75   $197.80  
  Purchase #4 $24.55   12.274%   $27.5633   $27.56   $27.55   $27.60  
  Purchase #5 $98.80   6.708%   $105.4275   $105.43   $105.45   $105.40  
  Purchase #6 $153.88   12.833%   $173.6274   $173.63   $173.65   $173.60  
  Purchase #7 $18.80   6.832%   $20.0844   $20.08   $20.10   $20.10  
  7 purchase totals = $678.77       $732.1669   $732.17   $732.20   $732.20