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 $208.37   11.266%   $231.845   $231.85   $231.85   $231.80  
  Purchase #2 $113.33   5.353%   $119.3966   $119.40   $119.40   $119.40  
  Purchase #3 $239.38   12.602%   $269.5467   $269.55   $269.55   $269.50  
  Purchase #4 $222.65   5.607%   $235.134   $235.13   $235.15   $235.10  
  Purchase #5 $44.74   5.670%   $47.2768   $47.28   $47.30   $47.30  
  Purchase #6 $184.94   4.622%   $193.4879   $193.49   $193.50   $193.50  
  Purchase #7 $177.95   7.304%   $190.9475   $190.95   $190.95   $190.90  
  7 purchase totals = $1,191.36       $1,287.6345   $1,287.65   $1,287.70   $1,287.50