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 $208.36   4.261%   $217.2382   $217.24   $217.25   $217.20  
  Purchase #2 $206.81   3.801%   $214.6708   $214.67   $214.65   $214.70  
  Purchase #3 $217.80   7.246%   $233.5818   $233.58   $233.60   $233.60  
  Purchase #4 $96.68   5.842%   $102.328   $102.33   $102.35   $102.30  
  Purchase #5 $147.99   10.601%   $163.6784   $163.68   $163.70   $163.70  
  Purchase #6 $175.58   11.693%   $196.1106   $196.11   $196.10   $196.10  
  Purchase #7 $169.94   5.465%   $179.2272   $179.23   $179.25   $179.20  
  7 purchase totals = $1,223.16       $1,306.8350   $1,306.84   $1,306.90   $1,306.80