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 $69.95   10.553%   $77.3318   $77.33   $77.35   $77.30  
  Purchase #2 $158.77   6.126%   $168.4963   $168.50   $168.50   $168.50  
  Purchase #3 $247.98   3.808%   $257.4231   $257.42   $257.40   $257.40  
  Purchase #4 $208.87   13.319%   $236.6894   $236.69   $236.70   $236.70  
  Purchase #5 $207.53   3.544%   $214.8849   $214.88   $214.90   $214.90  
  Purchase #6 $215.74   5.323%   $227.2238   $227.22   $227.20   $227.20  
  Purchase #7 $105.69   6.449%   $112.5059   $112.51   $112.50   $112.50  
  7 purchase totals = $1,214.53       $1,294.5552   $1,294.55   $1,294.55   $1,294.50