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 $218.51   3.798%   $226.809   $226.81   $226.80   $226.80  
  Purchase #2 $93.50   5.725%   $98.8529   $98.85   $98.85   $98.90  
  Purchase #3 $233.73   11.409%   $260.3963   $260.40   $260.40   $260.40  
  Purchase #4 $248.58   6.815%   $265.5207   $265.52   $265.50   $265.50  
  Purchase #5 $57.49   8.291%   $62.2565   $62.26   $62.25   $62.30  
  Purchase #6 $202.92   6.662%   $216.4385   $216.44   $216.45   $216.40  
  Purchase #7 $21.76   4.723%   $22.7877   $22.79   $22.80   $22.80  
  7 purchase totals = $1,076.49       $1,153.0616   $1,153.07   $1,153.05   $1,153.10