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 $247.92   5.708%   $262.0713   $262.07   $262.05   $262.10  
  Purchase #2 $108.95   9.810%   $119.638   $119.64   $119.65   $119.60  
  Purchase #3 $110.87   6.256%   $117.806   $117.81   $117.80   $117.80  
  Purchase #4 $173.30   10.479%   $191.4601   $191.46   $191.45   $191.50  
  Purchase #5 $76.60   3.218%   $79.065   $79.07   $79.05   $79.10  
  Purchase #6 $106.88   5.157%   $112.3918   $112.39   $112.40   $112.40  
  Purchase #7 $49.42   10.210%   $54.4658   $54.47   $54.45   $54.50  
  7 purchase totals = $873.94       $936.8980   $936.91   $936.85   $937.00