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 $61.46   4.271%   $64.085   $64.09   $64.10   $64.10  
  Purchase #2 $104.38   9.256%   $114.0414   $114.04   $114.05   $114.00  
  Purchase #3 $130.56   8.685%   $141.8991   $141.90   $141.90   $141.90  
  Purchase #4 $194.99   5.750%   $206.2019   $206.20   $206.20   $206.20  
  Purchase #5 $132.85   6.465%   $141.4388   $141.44   $141.45   $141.40  
  Purchase #6 $158.65   6.411%   $168.8211   $168.82   $168.80   $168.80  
  Purchase #7 $201.42   11.231%   $224.0415   $224.04   $224.05   $224.00  
  7 purchase totals = $984.31       $1,060.5288   $1,060.53   $1,060.55   $1,060.40