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 $207.30   9.174%   $226.3177   $226.32   $226.30   $226.30  
  Purchase #2 $103.98   6.746%   $110.9945   $110.99   $111.00   $111.00  
  Purchase #3 $44.93   12.418%   $50.5094   $50.51   $50.50   $50.50  
  Purchase #4 $124.65   3.719%   $129.2857   $129.29   $129.30   $129.30  
  Purchase #5 $136.42   3.832%   $141.6476   $141.65   $141.65   $141.60  
  Purchase #6 $114.62   9.457%   $125.4596   $125.46   $125.45   $125.50  
  Purchase #7 $220.32   8.874%   $239.8712   $239.87   $239.85   $239.90  
  7 purchase totals = $952.22       $1,024.0857   $1,024.09   $1,024.05   $1,024.10