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 $24.89   4.774%   $26.0782   $26.08   $26.10   $26.10  
  Purchase #2 $214.86   11.432%   $239.4228   $239.42   $239.40   $239.40  
  Purchase #3 $185.59   11.627%   $207.1685   $207.17   $207.15   $207.20  
  Purchase #4 $245.64   5.593%   $259.3786   $259.38   $259.40   $259.40  
  Purchase #5 $120.46   3.535%   $124.7183   $124.72   $124.70   $124.70  
  Purchase #6 $116.51   7.450%   $125.19   $125.19   $125.20   $125.20  
  Purchase #7 $37.98   8.464%   $41.1946   $41.19   $41.20   $41.20  
  7 purchase totals = $945.93       $1,023.1510   $1,023.15   $1,023.15   $1,023.20