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	$40.67	8.163%	$43.9899	$43.99	$44.00	$44.00
Purchase #2	$67.67	7.760%	$72.9212	$72.92	$72.90	$72.90
Purchase #3	$124.45	13.227%	$140.911	$140.91	$140.90	$140.90
Purchase #4	$250.39	11.851%	$280.0637	$280.06	$280.05	$280.10
Purchase #5	$123.25	8.490%	$133.7139	$133.71	$133.70	$133.70
Purchase #6	$233.30	13.295%	$264.3172	$264.32	$264.30	$264.30
Purchase #7	$72.62	4.587%	$75.9511	$75.95	$75.95	$76.00
7 purchase totals =	$912.35		$1,011.8680	$1,011.86	$1,011.80	$1,011.90