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 $65.61   4.581%   $68.6156   $68.62   $68.60   $68.60  
  Purchase #2 $205.27   4.625%   $214.7637   $214.76   $214.75   $214.80  
  Purchase #3 $224.97   9.447%   $246.2229   $246.22   $246.20   $246.20  
  Purchase #4 $82.66   4.167%   $86.1044   $86.10   $86.10   $86.10  
  Purchase #5 $115.77   7.349%   $124.2779   $124.28   $124.30   $124.30  
  Purchase #6 $121.77   11.526%   $135.8052   $135.81   $135.80   $135.80  
  Purchase #7 $235.63   9.671%   $258.4178   $258.42   $258.40   $258.40  
  7 purchase totals = $1,051.68       $1,134.2075   $1,134.21   $1,134.15   $1,134.20