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 $211.96   11.158%   $235.6105   $235.61   $235.60   $235.60  
  Purchase #2 $70.77   11.136%   $78.6509   $78.65   $78.65   $78.70  
  Purchase #3 $158.28   6.579%   $168.6932   $168.69   $168.70   $168.70  
  Purchase #4 $84.34   10.546%   $93.2345   $93.23   $93.25   $93.20  
  Purchase #5 $43.72   9.491%   $47.8695   $47.87   $47.85   $47.90  
  Purchase #6 $191.71   12.411%   $215.5031   $215.50   $215.50   $215.50  
  Purchase #7 $195.54   9.341%   $213.8054   $213.81   $213.80   $213.80  
  7 purchase totals = $956.32       $1,053.3671   $1,053.36   $1,053.35   $1,053.40