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 $152.70   6.112%   $162.033   $162.03   $162.05   $162.00  
  Purchase #2 $26.72   3.241%   $27.586   $27.59   $27.60   $27.60  
  Purchase #3 $5.89   3.381%   $6.0891   $6.09   $6.10   $6.10  
  Purchase #4 $240.93   6.694%   $257.0579   $257.06   $257.05   $257.10  
  Purchase #5 $59.38   6.458%   $63.2148   $63.21   $63.20   $63.20  
  Purchase #6 $68.33   3.215%   $70.5268   $70.53   $70.55   $70.50  
  Purchase #7 $245.33   6.651%   $261.6469   $261.65   $261.65   $261.60  
  7 purchase totals = $799.28       $848.1545   $848.16   $848.20   $848.10