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 $214.58   9.682%   $235.3556   $235.36   $235.35   $235.40  
  Purchase #2 $144.95   3.167%   $149.5406   $149.54   $149.55   $149.50  
  Purchase #3 $26.36   9.791%   $28.9409   $28.94   $28.95   $28.90  
  Purchase #4 $224.85   8.169%   $243.218   $243.22   $243.20   $243.20  
  Purchase #5 $186.37   3.357%   $192.6264   $192.63   $192.65   $192.60  
  Purchase #6 $158.62   9.418%   $173.5588   $173.56   $173.55   $173.60  
  Purchase #7 $150.69   6.809%   $160.9505   $160.95   $160.95   $161.00  
  7 purchase totals = $1,106.42       $1,184.1908   $1,184.20   $1,184.20   $1,184.20