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 $114.75   8.725%   $124.7619   $124.76   $124.75   $124.80  
  Purchase #2 $167.85   9.672%   $184.0845   $184.08   $184.10   $184.10  
  Purchase #3 $249.51   3.601%   $258.4949   $258.49   $258.50   $258.50  
  Purchase #4 $58.68   13.198%   $66.4246   $66.42   $66.40   $66.40  
  Purchase #5 $153.48   7.675%   $165.2596   $165.26   $165.25   $165.30  
  Purchase #6 $231.86   13.215%   $262.5003   $262.50   $262.50   $262.50  
  Purchase #7 $119.81   8.136%   $129.5577   $129.56   $129.55   $129.60  
  7 purchase totals = $1,095.94       $1,191.0835   $1,191.07   $1,191.05   $1,191.20