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 $85.58   11.668%   $95.5655   $95.57   $95.55   $95.60  
  Purchase #2 $203.87   12.758%   $229.8797   $229.88   $229.90   $229.90  
  Purchase #3 $112.84   10.182%   $124.3294   $124.33   $124.35   $124.30  
  Purchase #4 $141.68   7.106%   $151.7478   $151.75   $151.75   $151.70  
  Purchase #5 $101.33   12.507%   $114.0033   $114.00   $114.00   $114.00  
  Purchase #6 $106.88   10.391%   $117.9859   $117.99   $118.00   $118.00  
  Purchase #7 $46.54   12.180%   $52.2086   $52.21   $52.20   $52.20  
  7 purchase totals = $798.72       $885.7202   $885.73   $885.75   $885.70