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 $214.26   13.229%   $242.6045   $242.60   $242.60   $242.60  
  Purchase #2 $117.38   4.287%   $122.4121   $122.41   $122.40   $122.40  
  Purchase #3 $131.37   13.216%   $148.7319   $148.73   $148.75   $148.70  
  Purchase #4 $164.26   8.120%   $177.5979   $177.60   $177.60   $177.60  
  Purchase #5 $160.81   7.662%   $173.1313   $173.13   $173.15   $173.10  
  Purchase #6 $185.58   8.817%   $201.9426   $201.94   $201.95   $201.90  
  Purchase #7 $75.93   11.509%   $84.6688   $84.67   $84.65   $84.70  
  7 purchase totals = $1,049.59       $1,151.0891   $1,151.08   $1,151.10   $1,151.00