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 $194.83   5.718%   $205.9704   $205.97   $205.95   $206.00  
  Purchase #2 $155.51   10.107%   $171.2274   $171.23   $171.25   $171.20  
  Purchase #3 $192.98   11.172%   $214.5397   $214.54   $214.55   $214.50  
  Purchase #4 $214.89   8.792%   $233.7831   $233.78   $233.80   $233.80  
  Purchase #5 $123.58   3.167%   $127.4938   $127.49   $127.50   $127.50  
  Purchase #6 $49.85   10.435%   $55.0518   $55.05   $55.05   $55.10  
  Purchase #7 $146.25   6.387%   $155.591   $155.59   $155.60   $155.60  
  7 purchase totals = $1,077.89       $1,163.6572   $1,163.65   $1,163.70   $1,163.70