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 $105.68   6.312%   $112.3505   $112.35   $112.35   $112.40  
  Purchase #2 $207.36   10.388%   $228.9006   $228.90   $228.90   $228.90  
  Purchase #3 $62.84   8.134%   $67.9514   $67.95   $67.95   $68.00  
  Purchase #4 $98.49   6.557%   $104.948   $104.95   $104.95   $104.90  
  Purchase #5 $163.35   4.784%   $171.1647   $171.16   $171.15   $171.20  
  Purchase #6 $103.78   10.104%   $114.2659   $114.27   $114.25   $114.30  
  Purchase #7 $157.53   6.861%   $168.3381   $168.34   $168.35   $168.30  
  7 purchase totals = $899.03       $967.9192   $967.92   $967.90   $968.00