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 $60.67   13.686%   $68.9733   $68.97   $68.95   $69.00  
  Purchase #2 $240.47   9.132%   $262.4297   $262.43   $262.45   $262.40  
  Purchase #3 $140.87   9.457%   $154.1921   $154.19   $154.20   $154.20  
  Purchase #4 $219.43   11.380%   $244.4011   $244.40   $244.40   $244.40  
  Purchase #5 $56.68   5.756%   $59.9425   $59.94   $59.95   $59.90  
  Purchase #6 $188.66   4.151%   $196.4913   $196.49   $196.50   $196.50  
  Purchase #7 $121.83   6.361%   $129.5796   $129.58   $129.60   $129.60  
  7 purchase totals = $1,028.61       $1,116.0096   $1,116.00   $1,116.05   $1,116.00