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 $200.70   7.586%   $215.9251   $215.93   $215.95   $215.90  
  Purchase #2 $46.90   5.846%   $49.6418   $49.64   $49.65   $49.60  
  Purchase #3 $193.94   7.549%   $208.5805   $208.58   $208.60   $208.60  
  Purchase #4 $208.96   3.194%   $215.6342   $215.63   $215.65   $215.60  
  Purchase #5 $230.66   11.630%   $257.4858   $257.49   $257.50   $257.50  
  Purchase #6 $236.35   4.308%   $246.532   $246.53   $246.55   $246.50  
  Purchase #7 $8.71   9.597%   $9.5459   $9.55   $9.55   $9.50  
  7 purchase totals = $1,126.22       $1,203.3453   $1,203.35   $1,203.45   $1,203.20