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 $65.38   5.436%   $68.9341   $68.93   $68.95   $68.90  
  Purchase #2 $130.76   11.517%   $145.8196   $145.82   $145.80   $145.80  
  Purchase #3 $125.85   13.238%   $142.51   $142.51   $142.50   $142.50  
  Purchase #4 $182.54   10.430%   $201.5789   $201.58   $201.60   $201.60  
  Purchase #5 $92.37   9.589%   $101.2274   $101.23   $101.25   $101.20  
  Purchase #6 $104.61   13.348%   $118.5733   $118.57   $118.55   $118.60  
  Purchase #7 $240.83   10.190%   $265.3706   $265.37   $265.35   $265.40  
  7 purchase totals = $942.34       $1,044.0139   $1,044.01   $1,044.00   $1,044.00