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	$208.67	5.374%	$219.8839	$219.88	$219.90	$219.90
Purchase #2	$171.59	13.562%	$194.861	$194.86	$194.85	$194.90
Purchase #3	$25.62	13.643%	$29.1153	$29.12	$29.10	$29.10
Purchase #4	$113.85	8.665%	$123.7151	$123.72	$123.70	$123.70
Purchase #5	$35.70	13.198%	$40.4117	$40.41	$40.40	$40.40
Purchase #6	$11.45	13.853%	$13.0362	$13.04	$13.05	$13.00
Purchase #7	$111.60	4.120%	$116.1979	$116.20	$116.20	$116.20
7 purchase totals =	$678.48		$737.2211	$737.23	$737.20	$737.20