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 $196.87   5.694%   $208.0798   $208.08   $208.10   $208.10  
  Purchase #2 $25.41   3.549%   $26.3118   $26.31   $26.30   $26.30  
  Purchase #3 $60.54   5.571%   $63.9127   $63.91   $63.90   $63.90  
  Purchase #4 $93.29   11.122%   $103.6657   $103.67   $103.65   $103.70  
  Purchase #5 $112.94   8.282%   $122.2937   $122.29   $122.30   $122.30  
  Purchase #6 $136.88   4.773%   $143.4133   $143.41   $143.40   $143.40  
  Purchase #7 $195.32   3.563%   $202.2793   $202.28   $202.30   $202.30  
  7 purchase totals = $821.25       $869.9563   $869.95   $869.95   $870.00