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 $247.70   5.238%   $260.6745   $260.67   $260.65   $260.70  
  Purchase #2 $176.41   12.522%   $198.5001   $198.50   $198.50   $198.50  
  Purchase #3 $186.39   12.474%   $209.6403   $209.64   $209.65   $209.60  
  Purchase #4 $124.60   8.743%   $135.4938   $135.49   $135.50   $135.50  
  Purchase #5 $58.42   6.529%   $62.2342   $62.23   $62.25   $62.20  
  Purchase #6 $74.33   13.767%   $84.563   $84.56   $84.55   $84.60  
  Purchase #7 $183.80   10.345%   $202.8141   $202.81   $202.80   $202.80  
  7 purchase totals = $1,051.65       $1,153.9200   $1,153.90   $1,153.90   $1,153.90