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 $61.55   6.749%   $65.704   $65.70   $65.70   $65.70  
  Purchase #2 $239.29   9.520%   $262.0704   $262.07   $262.05   $262.10  
  Purchase #3 $105.45   8.393%   $114.3004   $114.30   $114.30   $114.30  
  Purchase #4 $222.91   11.552%   $248.6606   $248.66   $248.65   $248.70  
  Purchase #5 $171.65   4.544%   $179.4498   $179.45   $179.45   $179.40  
  Purchase #6 $228.87   11.350%   $254.8467   $254.85   $254.85   $254.80  
  Purchase #7 $21.66   5.300%   $22.808   $22.81   $22.80   $22.80  
  7 purchase totals = $1,051.38       $1,147.8399   $1,147.84   $1,147.80   $1,147.80