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 $173.51   12.427%   $195.0721   $195.07   $195.05   $195.10  
  Purchase #2 $44.39   5.737%   $46.9367   $46.94   $46.95   $46.90  
  Purchase #3 $250.78   7.643%   $269.9471   $269.95   $269.95   $269.90  
  Purchase #4 $85.34   6.225%   $90.6524   $90.65   $90.65   $90.70  
  Purchase #5 $215.85   7.827%   $232.7446   $232.74   $232.75   $232.70  
  Purchase #6 $49.72   9.634%   $54.51   $54.51   $54.50   $54.50  
  Purchase #7 $52.91   10.339%   $58.3804   $58.38   $58.40   $58.40  
  7 purchase totals = $872.50       $948.2433   $948.24   $948.25   $948.20