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 $192.95   7.113%   $206.6745   $206.67   $206.65   $206.70  
  Purchase #2 $224.81   11.250%   $250.1011   $250.10   $250.10   $250.10  
  Purchase #3 $95.35   3.413%   $98.6043   $98.60   $98.60   $98.60  
  Purchase #4 $5.26   9.268%   $5.7475   $5.75   $5.75   $5.70  
  Purchase #5 $214.67   6.671%   $228.9906   $228.99   $229.00   $229.00  
  Purchase #6 $185.37   12.597%   $208.7211   $208.72   $208.70   $208.70  
  Purchase #7 $24.75   8.785%   $26.9243   $26.92   $26.90   $26.90  
  7 purchase totals = $943.16       $1,025.7634   $1,025.75   $1,025.70   $1,025.70