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 $58.29   9.562%   $63.8637   $63.86   $63.85   $63.90  
  Purchase #2 $207.88   7.339%   $223.1363   $223.14   $223.15   $223.10  
  Purchase #3 $239.48   9.613%   $262.5012   $262.50   $262.50   $262.50  
  Purchase #4 $81.89   12.239%   $91.9125   $91.91   $91.90   $91.90  
  Purchase #5 $91.50   4.570%   $95.6816   $95.68   $95.70   $95.70  
  Purchase #6 $94.99   8.615%   $103.1734   $103.17   $103.15   $103.20  
  Purchase #7 $107.93   10.412%   $119.1677   $119.17   $119.15   $119.20  
  7 purchase totals = $881.96       $959.4364   $959.43   $959.40   $959.50