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 $68.98   11.506%   $76.9168   $76.92   $76.90   $76.90  
  Purchase #2 $61.26   3.189%   $63.2136   $63.21   $63.20   $63.20  
  Purchase #3 $193.68   5.826%   $204.9638   $204.96   $204.95   $205.00  
  Purchase #4 $202.63   13.712%   $230.4146   $230.41   $230.40   $230.40  
  Purchase #5 $241.83   7.335%   $259.5682   $259.57   $259.55   $259.60  
  Purchase #6 $13.44   3.334%   $13.8881   $13.89   $13.90   $13.90  
  Purchase #7 $222.50   10.673%   $246.2474   $246.25   $246.25   $246.20  
  7 purchase totals = $1,004.32       $1,095.2125   $1,095.21   $1,095.15   $1,095.20