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 $13.94   5.807%   $14.7495   $14.75   $14.75   $14.70  
  Purchase #2 $202.92   11.180%   $225.6065   $225.61   $225.60   $225.60  
  Purchase #3 $31.84   9.181%   $34.7632   $34.76   $34.75   $34.80  
  Purchase #4 $222.84   3.841%   $231.3993   $231.40   $231.40   $231.40  
  Purchase #5 $163.55   11.266%   $181.9755   $181.98   $182.00   $182.00  
  Purchase #6 $179.91   3.267%   $185.7877   $185.79   $185.80   $185.80  
  Purchase #7 $136.58   4.767%   $143.0908   $143.09   $143.10   $143.10  
  7 purchase totals = $951.58       $1,017.3725   $1,017.38   $1,017.40   $1,017.40