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 $82.59   11.752%   $92.296   $92.30   $92.30   $92.30  
  Purchase #2 $162.61   8.658%   $176.6888   $176.69   $176.70   $176.70  
  Purchase #3 $19.63   12.493%   $22.0824   $22.08   $22.10   $22.10  
  Purchase #4 $16.70   7.742%   $17.9929   $17.99   $18.00   $18.00  
  Purchase #5 $158.57   3.866%   $164.7003   $164.70   $164.70   $164.70  
  Purchase #6 $159.58   5.459%   $168.2915   $168.29   $168.30   $168.30  
  Purchase #7 $75.49   7.221%   $80.9411   $80.94   $80.95   $80.90  
  7 purchase totals = $675.17       $722.9930   $722.99   $723.05   $723.00