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	$41.63	4.395%	$43.4596	$43.46	$43.45	$43.50
Purchase #2	$248.55	12.770%	$280.2898	$280.29	$280.30	$280.30
Purchase #3	$17.81	12.706%	$20.0729	$20.07	$20.05	$20.10
Purchase #4	$184.32	4.127%	$191.9269	$191.93	$191.95	$191.90
Purchase #5	$61.62	4.695%	$64.5131	$64.51	$64.50	$64.50
Purchase #6	$179.88	9.155%	$196.348	$196.35	$196.35	$196.30
Purchase #7	$166.47	13.490%	$188.9268	$188.93	$188.95	$188.90
7 purchase totals =	$900.28		$985.5371	$985.54	$985.55	$985.50