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 $24.98   4.408%   $26.0811   $26.08   $26.10   $26.10  
  Purchase #2 $175.43   13.358%   $198.8639   $198.86   $198.85   $198.90  
  Purchase #3 $11.90   10.300%   $13.1257   $13.13   $13.15   $13.10  
  Purchase #4 $229.41   10.588%   $253.6999   $253.70   $253.70   $253.70  
  Purchase #5 $65.92   3.285%   $68.0855   $68.09   $68.10   $68.10  
  Purchase #6 $85.68   7.727%   $92.3005   $92.30   $92.30   $92.30  
  Purchase #7 $62.35   3.722%   $64.6707   $64.67   $64.65   $64.70  
  7 purchase totals = $655.67       $716.8273   $716.83   $716.85   $716.90