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 $63.71   3.152%   $65.7181   $65.72   $65.70   $65.70  
  Purchase #2 $161.92   10.389%   $178.7419   $178.74   $178.75   $178.70  
  Purchase #3 $97.62   5.577%   $103.0643   $103.06   $103.05   $103.10  
  Purchase #4 $229.45   8.314%   $248.5265   $248.53   $248.55   $248.50  
  Purchase #5 $123.88   11.435%   $138.0457   $138.05   $138.05   $138.00  
  Purchase #6 $242.88   4.674%   $254.2322   $254.23   $254.25   $254.20  
  Purchase #7 $197.45   5.773%   $208.8488   $208.85   $208.85   $208.80  
  7 purchase totals = $1,116.91       $1,197.1775   $1,197.18   $1,197.20   $1,197.00