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 $61.42   7.211%   $65.849   $65.85   $65.85   $65.80  
  Purchase #2 $167.97   5.189%   $176.686   $176.69   $176.70   $176.70  
  Purchase #3 $203.81   8.564%   $221.2643   $221.26   $221.25   $221.30  
  Purchase #4 $91.40   5.103%   $96.0641   $96.06   $96.05   $96.10  
  Purchase #5 $7.70   5.169%   $8.098   $8.10   $8.10   $8.10  
  Purchase #6 $29.89   13.333%   $33.8752   $33.88   $33.90   $33.90  
  Purchase #7 $117.47   13.826%   $133.7114   $133.71   $133.70   $133.70  
  7 purchase totals = $679.66       $735.5480   $735.55   $735.55   $735.60