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 $68.83   7.441%   $73.9516   $73.95   $73.95   $74.00  
  Purchase #2 $231.69   6.780%   $247.3986   $247.40   $247.40   $247.40  
  Purchase #3 $15.77   12.458%   $17.7346   $17.73   $17.75   $17.70  
  Purchase #4 $250.75   6.491%   $267.0262   $267.03   $267.05   $267.00  
  Purchase #5 $134.34   9.379%   $146.9397   $146.94   $146.95   $146.90  
  Purchase #6 $181.50   4.661%   $189.9597   $189.96   $189.95   $190.00  
  Purchase #7 $204.81   3.714%   $212.4166   $212.42   $212.40   $212.40  
  7 purchase totals = $1,087.69       $1,155.4270   $1,155.43   $1,155.45   $1,155.40