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 $60.87   3.432%   $62.9591   $62.96   $62.95   $63.00  
  Purchase #2 $134.93   13.687%   $153.3979   $153.40   $153.40   $153.40  
  Purchase #3 $161.83   10.714%   $179.1685   $179.17   $179.15   $179.20  
  Purchase #4 $164.30   11.857%   $183.7811   $183.78   $183.80   $183.80  
  Purchase #5 $228.96   3.817%   $237.6994   $237.70   $237.70   $237.70  
  Purchase #6 $134.85   6.493%   $143.6058   $143.61   $143.60   $143.60  
  Purchase #7 $78.37   9.301%   $85.6592   $85.66   $85.65   $85.70  
  7 purchase totals = $964.11       $1,046.2710   $1,046.28   $1,046.25   $1,046.40