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 $71.88   6.841%   $76.7973   $76.80   $76.80   $76.80  
  Purchase #2 $41.46   6.474%   $44.1441   $44.14   $44.15   $44.10  
  Purchase #3 $92.90   13.579%   $105.5149   $105.51   $105.50   $105.50  
  Purchase #4 $248.27   3.116%   $256.0061   $256.01   $256.00   $256.00  
  Purchase #5 $211.25   13.289%   $239.323   $239.32   $239.30   $239.30  
  Purchase #6 $148.31   5.230%   $156.0666   $156.07   $156.05   $156.10  
  Purchase #7 $195.50   11.357%   $217.7029   $217.70   $217.70   $217.70  
  7 purchase totals = $1,009.57       $1,095.5549   $1,095.55   $1,095.50   $1,095.50