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 $181.61   13.256%   $205.6842   $205.68   $205.70   $205.70  
  Purchase #2 $229.62   6.329%   $244.1526   $244.15   $244.15   $244.20  
  Purchase #3 $201.34   11.291%   $224.0733   $224.07   $224.05   $224.10  
  Purchase #4 $211.88   12.197%   $237.723   $237.72   $237.70   $237.70  
  Purchase #5 $66.93   3.168%   $69.0503   $69.05   $69.05   $69.10  
  Purchase #6 $19.46   7.218%   $20.8646   $20.86   $20.85   $20.90  
  Purchase #7 $183.95   4.647%   $192.4982   $192.50   $192.50   $192.50  
  7 purchase totals = $1,094.79       $1,194.0462   $1,194.03   $1,194.00   $1,194.20