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 $194.25   7.333%   $208.4944   $208.49   $208.50   $208.50  
  Purchase #2 $191.51   3.161%   $197.5636   $197.56   $197.55   $197.60  
  Purchase #3 $203.58   6.329%   $216.4646   $216.46   $216.45   $216.50  
  Purchase #4 $113.75   5.224%   $119.6923   $119.69   $119.70   $119.70  
  Purchase #5 $135.82   9.195%   $148.3086   $148.31   $148.30   $148.30  
  Purchase #6 $144.63   5.492%   $152.5731   $152.57   $152.55   $152.60  
  Purchase #7 $23.63   10.229%   $26.0471   $26.05   $26.05   $26.00  
  7 purchase totals = $1,007.17       $1,069.1437   $1,069.13   $1,069.10   $1,069.20