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 $244.99   7.223%   $262.6856   $262.69   $262.70   $262.70  
  Purchase #2 $115.87   10.679%   $128.2438   $128.24   $128.25   $128.20  
  Purchase #3 $120.64   10.608%   $133.4375   $133.44   $133.45   $133.40  
  Purchase #4 $203.98   12.170%   $228.8044   $228.80   $228.80   $228.80  
  Purchase #5 $242.84   7.681%   $261.4925   $261.49   $261.50   $261.50  
  Purchase #6 $47.68   11.722%   $53.269   $53.27   $53.25   $53.30  
  Purchase #7 $36.94   7.406%   $39.6758   $39.68   $39.70   $39.70  
  7 purchase totals = $1,012.94       $1,107.6086   $1,107.61   $1,107.65   $1,107.60