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 $69.80   5.356%   $73.5385   $73.54   $73.55   $73.50  
  Purchase #2 $201.36   6.362%   $214.1705   $214.17   $214.15   $214.20  
  Purchase #3 $11.89   11.421%   $13.248   $13.25   $13.25   $13.20  
  Purchase #4 $70.59   11.807%   $78.9246   $78.92   $78.90   $78.90  
  Purchase #5 $5.42   6.465%   $5.7704   $5.77   $5.75   $5.80  
  Purchase #6 $196.64   6.689%   $209.7932   $209.79   $209.80   $209.80  
  Purchase #7 $145.44   12.379%   $163.444   $163.44   $163.45   $163.40  
  7 purchase totals = $701.14       $758.8892   $758.88   $758.85   $758.80