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 $60.41   3.353%   $62.4355   $62.44   $62.45   $62.40  
  Purchase #2 $217.83   8.622%   $236.6113   $236.61   $236.60   $236.60  
  Purchase #3 $154.55   8.578%   $167.8073   $167.81   $167.80   $167.80  
  Purchase #4 $243.72   5.625%   $257.4293   $257.43   $257.45   $257.40  
  Purchase #5 $94.76   10.839%   $105.031   $105.03   $105.05   $105.00  
  Purchase #6 $80.32   7.528%   $86.3665   $86.37   $86.35   $86.40  
  Purchase #7 $31.68   9.419%   $34.6639   $34.66   $34.65   $34.70  
  7 purchase totals = $883.27       $950.3448   $950.35   $950.35   $950.30