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 $206.35   9.572%   $226.1018   $226.10   $226.10   $226.10  
  Purchase #2 $199.81   7.567%   $214.9296   $214.93   $214.95   $214.90  
  Purchase #3 $22.46   7.536%   $24.1526   $24.15   $24.15   $24.20  
  Purchase #4 $44.99   9.270%   $49.1606   $49.16   $49.15   $49.20  
  Purchase #5 $186.85   3.247%   $192.917   $192.92   $192.90   $192.90  
  Purchase #6 $146.33   7.381%   $157.1306   $157.13   $157.15   $157.10  
  Purchase #7 $150.93   4.663%   $157.9679   $157.97   $157.95   $158.00  
  7 purchase totals = $957.72       $1,022.3601   $1,022.36   $1,022.35   $1,022.40