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 $107.95   6.460%   $114.9236   $114.92   $114.90   $114.90  
  Purchase #2 $217.65   9.273%   $237.8327   $237.83   $237.85   $237.80  
  Purchase #3 $60.32   3.739%   $62.5754   $62.58   $62.60   $62.60  
  Purchase #4 $211.36   6.319%   $224.7158   $224.72   $224.70   $224.70  
  Purchase #5 $167.48   6.149%   $177.7783   $177.78   $177.80   $177.80  
  Purchase #6 $207.45   3.665%   $215.053   $215.05   $215.05   $215.10  
  Purchase #7 $163.79   6.106%   $173.791   $173.79   $173.80   $173.80  
  7 purchase totals = $1,136.00       $1,206.6698   $1,206.67   $1,206.70   $1,206.70