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 $208.83   13.871%   $237.7968   $237.80   $237.80   $237.80  
  Purchase #2 $114.76   12.849%   $129.5055   $129.51   $129.50   $129.50  
  Purchase #3 $98.78   12.673%   $111.2984   $111.30   $111.30   $111.30  
  Purchase #4 $97.52   5.788%   $103.1645   $103.16   $103.15   $103.20  
  Purchase #5 $173.27   5.151%   $182.1951   $182.20   $182.20   $182.20  
  Purchase #6 $242.62   3.629%   $251.4247   $251.42   $251.40   $251.40  
  Purchase #7 $235.98   4.767%   $247.2292   $247.23   $247.25   $247.20  
  7 purchase totals = $1,171.76       $1,262.6142   $1,262.62   $1,262.60   $1,262.60