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 $82.76   4.797%   $86.73   $86.73   $86.75   $86.70  
  Purchase #2 $182.42   6.833%   $194.8848   $194.88   $194.90   $194.90  
  Purchase #3 $133.73   9.584%   $146.5467   $146.55   $146.55   $146.50  
  Purchase #4 $179.34   10.522%   $198.2102   $198.21   $198.20   $198.20  
  Purchase #5 $234.34   6.223%   $248.923   $248.92   $248.90   $248.90  
  Purchase #6 $112.60   12.429%   $126.5951   $126.60   $126.60   $126.60  
  Purchase #7 $104.54   9.670%   $114.649   $114.65   $114.65   $114.60  
  7 purchase totals = $1,029.73       $1,116.5388   $1,116.54   $1,116.55   $1,116.40