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 $204.81   5.588%   $216.2548   $216.25   $216.25   $216.30  
  Purchase #2 $119.81   8.388%   $129.8597   $129.86   $129.85   $129.90  
  Purchase #3 $44.61   3.319%   $46.0906   $46.09   $46.10   $46.10  
  Purchase #4 $105.73   3.240%   $109.1557   $109.16   $109.15   $109.20  
  Purchase #5 $213.95   13.267%   $242.3347   $242.33   $242.35   $242.30  
  Purchase #6 $237.68   6.334%   $252.7347   $252.73   $252.75   $252.70  
  Purchase #7 $115.47   6.772%   $123.2896   $123.29   $123.30   $123.30  
  7 purchase totals = $1,042.06       $1,119.7198   $1,119.71   $1,119.75   $1,119.80