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 $84.74   13.169%   $95.8994   $95.90   $95.90   $95.90  
  Purchase #2 $25.25   3.286%   $26.0797   $26.08   $26.10   $26.10  
  Purchase #3 $67.28   4.640%   $70.4018   $70.40   $70.40   $70.40  
  Purchase #4 $185.45   4.460%   $193.7211   $193.72   $193.70   $193.70  
  Purchase #5 $27.46   10.691%   $30.3957   $30.40   $30.40   $30.40  
  Purchase #6 $166.90   5.827%   $176.6253   $176.63   $176.65   $176.60  
  Purchase #7 $102.47   13.306%   $116.1047   $116.10   $116.10   $116.10  
  7 purchase totals = $659.55       $709.2277   $709.23   $709.25   $709.20