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 $83.71   11.730%   $93.5292   $93.53   $93.55   $93.50  
  Purchase #2 $148.75   5.356%   $156.7171   $156.72   $156.70   $156.70  
  Purchase #3 $111.76   6.565%   $119.097   $119.10   $119.10   $119.10  
  Purchase #4 $166.90   10.241%   $183.9922   $183.99   $184.00   $184.00  
  Purchase #5 $87.65   10.381%   $96.7489   $96.75   $96.75   $96.70  
  Purchase #6 $248.78   4.767%   $260.6393   $260.64   $260.65   $260.60  
  Purchase #7 $106.67   7.587%   $114.7631   $114.76   $114.75   $114.80  
  7 purchase totals = $954.22       $1,025.4868   $1,025.49   $1,025.50   $1,025.40