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 $151.49   3.307%   $156.4998   $156.50   $156.50   $156.50  
  Purchase #2 $78.38   7.483%   $84.2452   $84.25   $84.25   $84.20  
  Purchase #3 $54.36   13.617%   $61.7622   $61.76   $61.75   $61.80  
  Purchase #4 $82.26   13.430%   $93.3075   $93.31   $93.30   $93.30  
  Purchase #5 $211.92   7.380%   $227.5597   $227.56   $227.55   $227.60  
  Purchase #6 $168.54   10.478%   $186.1996   $186.20   $186.20   $186.20  
  Purchase #7 $182.70   13.284%   $206.9699   $206.97   $206.95   $207.00  
  7 purchase totals = $929.65       $1,016.5439   $1,016.55   $1,016.50   $1,016.60