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 $126.25   6.613%   $134.5989   $134.60   $134.60   $134.60  
  Purchase #2 $227.93   3.511%   $235.9326   $235.93   $235.95   $235.90  
  Purchase #3 $114.63   6.589%   $122.183   $122.18   $122.20   $122.20  
  Purchase #4 $183.67   8.822%   $199.8734   $199.87   $199.85   $199.90  
  Purchase #5 $18.90   9.828%   $20.7575   $20.76   $20.75   $20.80  
  Purchase #6 $204.57   4.458%   $213.6897   $213.69   $213.70   $213.70  
  Purchase #7 $192.70   5.403%   $203.1116   $203.11   $203.10   $203.10  
  7 purchase totals = $1,068.65       $1,130.1467   $1,130.14   $1,130.15   $1,130.20