As soon as you start rounding you purposely enter a level of error into
the spreadsheet.

Essentially, you are telling Excel you are comfortable with an error as
long as it is less that a certain amount. Adding numerous errors which,
by themselves, are immaterial could aggregate to a material error, but
this would be statistically improbable. For every number, there is a
statistically equal chance of rounding up or down. By the same token,
it is statistically improbable that for any given number of roundings
exactly half rounded up and half rounded down. (Which is what must
occur for the sum of the rounded detail to match the rounded total.)

Basically, you have to decide if the 50 cents is important enough to
concern your spreadsheet users. My experience tells me someone always
catches the 50 cents and wants to use it to cast doubts on the veracity
of the spreadsheet as a whole. For this reason, I would note the item
as '$.50 difference due to rounding' in a comment to small text box and
carry on.