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 $95.37   9.851%   $104.7649   $104.76   $104.75   $104.80  
  Purchase #2 $226.34   3.399%   $234.0333   $234.03   $234.05   $234.00  
  Purchase #3 $207.81   5.184%   $218.5829   $218.58   $218.60   $218.60  
  Purchase #4 $9.48   12.184%   $10.635   $10.64   $10.65   $10.60  
  Purchase #5 $232.95   7.501%   $250.4236   $250.42   $250.40   $250.40  
  Purchase #6 $234.42   13.817%   $266.8098   $266.81   $266.80   $266.80  
  Purchase #7 $166.31   5.501%   $175.4587   $175.46   $175.45   $175.50  
  7 purchase totals = $1,172.68       $1,260.7082   $1,260.70   $1,260.70   $1,260.70