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 $224.58   5.505%   $236.9431   $236.94   $236.95   $236.90  
  Purchase #2 $208.90   3.740%   $216.7129   $216.71   $216.70   $216.70  
  Purchase #3 $8.59   10.371%   $9.4809   $9.48   $9.50   $9.50  
  Purchase #4 $26.64   13.749%   $30.3027   $30.30   $30.30   $30.30  
  Purchase #5 $150.49   5.203%   $158.32   $158.32   $158.30   $158.30  
  Purchase #6 $65.54   3.469%   $67.8136   $67.81   $67.80   $67.80  
  Purchase #7 $6.45   12.104%   $7.2307   $7.23   $7.25   $7.20  
  7 purchase totals = $691.19       $726.8039   $726.79   $726.80   $726.70