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 $245.51   6.706%   $261.9739   $261.97   $261.95   $262.00  
  Purchase #2 $102.68   4.355%   $107.1517   $107.15   $107.15   $107.20  
  Purchase #3 $194.65   10.290%   $214.6795   $214.68   $214.70   $214.70  
  Purchase #4 $56.51   7.124%   $60.5358   $60.54   $60.55   $60.50  
  Purchase #5 $233.66   11.612%   $260.7926   $260.79   $260.80   $260.80  
  Purchase #6 $136.25   11.215%   $151.5304   $151.53   $151.55   $151.50  
  Purchase #7 $41.99   6.400%   $44.6774   $44.68   $44.70   $44.70  
  7 purchase totals = $1,011.25       $1,101.3413   $1,101.34   $1,101.40   $1,101.40