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 $42.46   5.319%   $44.7184   $44.72   $44.70   $44.70  
  Purchase #2 $229.52   8.114%   $248.1433   $248.14   $248.15   $248.10  
  Purchase #3 $244.36   5.337%   $257.4015   $257.40   $257.40   $257.40  
  Purchase #4 $57.89   3.678%   $60.0192   $60.02   $60.00   $60.00  
  Purchase #5 $151.81   3.423%   $157.0065   $157.01   $157.00   $157.00  
  Purchase #6 $248.98   8.478%   $270.0885   $270.09   $270.10   $270.10  
  Purchase #7 $147.69   13.702%   $167.9265   $167.93   $167.95   $167.90  
  7 purchase totals = $1,122.71       $1,205.3039   $1,205.31   $1,205.30   $1,205.20