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 $23.86   8.811%   $25.9623   $25.96   $25.95   $26.00  
  Purchase #2 $169.95   9.824%   $186.6459   $186.65   $186.65   $186.60  
  Purchase #3 $75.68   13.433%   $85.8461   $85.85   $85.85   $85.80  
  Purchase #4 $183.34   6.407%   $195.0866   $195.09   $195.10   $195.10  
  Purchase #5 $122.48   3.563%   $126.844   $126.84   $126.85   $126.80  
  Purchase #6 $185.95   6.422%   $197.8917   $197.89   $197.90   $197.90  
  Purchase #7 $105.93   7.498%   $113.8726   $113.87   $113.85   $113.90  
  7 purchase totals = $867.19       $932.1492   $932.15   $932.15   $932.10