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 $202.37   13.455%   $229.5989   $229.60   $229.60   $229.60  
  Purchase #2 $148.59   9.565%   $162.8026   $162.80   $162.80   $162.80  
  Purchase #3 $119.54   5.641%   $126.2833   $126.28   $126.30   $126.30  
  Purchase #4 $146.81   5.112%   $154.3149   $154.31   $154.30   $154.30  
  Purchase #5 $164.37   11.375%   $183.0671   $183.07   $183.05   $183.10  
  Purchase #6 $180.63   8.617%   $196.1949   $196.19   $196.20   $196.20  
  Purchase #7 $19.56   12.725%   $22.049   $22.05   $22.05   $22.00  
  7 purchase totals = $981.87       $1,074.3107   $1,074.30   $1,074.30   $1,074.30