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 $181.36   10.830%   $201.0013   $201.00   $201.00   $201.00  
  Purchase #2 $26.79   6.684%   $28.5806   $28.58   $28.60   $28.60  
  Purchase #3 $65.51   4.539%   $68.4835   $68.48   $68.50   $68.50  
  Purchase #4 $96.77   12.874%   $109.2282   $109.23   $109.25   $109.20  
  Purchase #5 $137.73   9.832%   $151.2716   $151.27   $151.25   $151.30  
  Purchase #6 $241.37   4.451%   $252.1134   $252.11   $252.10   $252.10  
  Purchase #7 $207.89   3.371%   $214.898   $214.90   $214.90   $214.90  
  7 purchase totals = $957.42       $1,025.5766   $1,025.57   $1,025.60   $1,025.60