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 $221.66   5.388%   $233.603   $233.60   $233.60   $233.60  
  Purchase #2 $141.56   5.871%   $149.871   $149.87   $149.85   $149.90  
  Purchase #3 $33.78   4.258%   $35.2184   $35.22   $35.20   $35.20  
  Purchase #4 $87.75   10.602%   $97.0533   $97.05   $97.05   $97.10  
  Purchase #5 $59.92   13.111%   $67.7761   $67.78   $67.80   $67.80  
  Purchase #6 $201.44   4.154%   $209.8078   $209.81   $209.80   $209.80  
  Purchase #7 $109.46   4.406%   $114.2828   $114.28   $114.30   $114.30  
  7 purchase totals = $855.57       $907.6124   $907.61   $907.60   $907.70