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 $106.60   10.785%   $118.0968   $118.10   $118.10   $118.10  
  Purchase #2 $197.41   9.718%   $216.5943   $216.59   $216.60   $216.60  
  Purchase #3 $109.77   4.131%   $114.3046   $114.30   $114.30   $114.30  
  Purchase #4 $188.81   5.774%   $199.7119   $199.71   $199.70   $199.70  
  Purchase #5 $85.25   11.614%   $95.1509   $95.15   $95.15   $95.20  
  Purchase #6 $248.76   3.413%   $257.2502   $257.25   $257.25   $257.30  
  Purchase #7 $55.85   9.441%   $61.1228   $61.12   $61.10   $61.10  
  7 purchase totals = $992.45       $1,062.2315   $1,062.22   $1,062.20   $1,062.30