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 $114.49   3.347%   $118.322   $118.32   $118.30   $118.30  
  Purchase #2 $247.63   10.799%   $274.3716   $274.37   $274.35   $274.40  
  Purchase #3 $153.61   6.607%   $163.759   $163.76   $163.75   $163.80  
  Purchase #4 $214.26   11.466%   $238.8271   $238.83   $238.85   $238.80  
  Purchase #5 $185.35   9.610%   $203.1621   $203.16   $203.15   $203.20  
  Purchase #6 $123.59   8.852%   $134.5302   $134.53   $134.55   $134.50  
  Purchase #7 $64.48   8.850%   $70.1865   $70.19   $70.20   $70.20  
  7 purchase totals = $1,103.41       $1,203.1585   $1,203.16   $1,203.15   $1,203.20