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 $44.64   8.301%   $48.3456   $48.35   $48.35   $48.30  
  Purchase #2 $114.47   4.547%   $119.675   $119.68   $119.70   $119.70  
  Purchase #3 $226.65   4.122%   $235.9925   $235.99   $236.00   $236.00  
  Purchase #4 $190.59   12.614%   $214.631   $214.63   $214.65   $214.60  
  Purchase #5 $20.93   12.422%   $23.5299   $23.53   $23.55   $23.50  
  Purchase #6 $5.27   9.316%   $5.761   $5.76   $5.75   $5.80  
  Purchase #7 $51.38   3.456%   $53.1557   $53.16   $53.15   $53.20  
  7 purchase totals = $653.93       $701.0907   $701.10   $701.15   $701.10