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 $193.36   4.337%   $201.746   $201.75   $201.75   $201.70  
  Purchase #2 $57.75   10.190%   $63.6347   $63.63   $63.65   $63.60  
  Purchase #3 $208.68   5.771%   $220.7229   $220.72   $220.70   $220.70  
  Purchase #4 $237.81   8.246%   $257.4198   $257.42   $257.40   $257.40  
  Purchase #5 $99.37   10.606%   $109.9092   $109.91   $109.90   $109.90  
  Purchase #6 $102.37   11.476%   $114.118   $114.12   $114.10   $114.10  
  Purchase #7 $188.75   9.683%   $207.0267   $207.03   $207.05   $207.00  
  7 purchase totals = $1,088.09       $1,174.5773   $1,174.58   $1,174.55   $1,174.40