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 $178.49   11.393%   $198.8254   $198.83   $198.85   $198.80  
  Purchase #2 $209.89   6.524%   $223.5832   $223.58   $223.60   $223.60  
  Purchase #3 $63.66   4.850%   $66.7475   $66.75   $66.75   $66.70  
  Purchase #4 $179.72   7.722%   $193.598   $193.60   $193.60   $193.60  
  Purchase #5 $74.28   11.116%   $82.537   $82.54   $82.55   $82.50  
  Purchase #6 $118.54   12.367%   $133.1998   $133.20   $133.20   $133.20  
  Purchase #7 $227.27   9.208%   $248.197   $248.20   $248.20   $248.20  
  7 purchase totals = $1,051.85       $1,146.6879   $1,146.70   $1,146.75   $1,146.60