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 $246.68   6.477%   $262.6575   $262.66   $262.65   $262.70  
  Purchase #2 $174.77   3.554%   $180.9813   $180.98   $181.00   $181.00  
  Purchase #3 $107.25   3.392%   $110.8879   $110.89   $110.90   $110.90  
  Purchase #4 $143.83   10.699%   $159.2184   $159.22   $159.20   $159.20  
  Purchase #5 $197.30   13.597%   $224.1269   $224.13   $224.15   $224.10  
  Purchase #6 $175.85   5.602%   $185.7011   $185.70   $185.70   $185.70  
  Purchase #7 $49.86   7.525%   $53.612   $53.61   $53.60   $53.60  
  7 purchase totals = $1,095.54       $1,177.1851   $1,177.19   $1,177.20   $1,177.20