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 $143.64   6.522%   $153.0082   $153.01   $153.00   $153.00  
  Purchase #2 $89.82   4.291%   $93.6742   $93.67   $93.65   $93.70  
  Purchase #3 $88.37   9.615%   $96.8668   $96.87   $96.85   $96.90  
  Purchase #4 $249.62   4.715%   $261.3896   $261.39   $261.40   $261.40  
  Purchase #5 $196.70   9.244%   $214.8829   $214.88   $214.90   $214.90  
  Purchase #6 $117.32   8.169%   $126.9039   $126.90   $126.90   $126.90  
  Purchase #7 $198.43   8.457%   $215.2112   $215.21   $215.20   $215.20  
  7 purchase totals = $1,083.90       $1,161.9368   $1,161.93   $1,161.90   $1,162.00