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 $196.76   8.760%   $213.9962   $214.00   $214.00   $214.00  
  Purchase #2 $80.86   7.286%   $86.7515   $86.75   $86.75   $86.80  
  Purchase #3 $236.44   12.833%   $266.7823   $266.78   $266.80   $266.80  
  Purchase #4 $246.72   10.592%   $272.8526   $272.85   $272.85   $272.90  
  Purchase #5 $226.95   13.611%   $257.8402   $257.84   $257.85   $257.80  
  Purchase #6 $103.65   11.547%   $115.6185   $115.62   $115.60   $115.60  
  Purchase #7 $30.27   8.677%   $32.8965   $32.90   $32.90   $32.90  
  7 purchase totals = $1,121.65       $1,246.7378   $1,246.74   $1,246.75   $1,246.80