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	$67.33	6.634%	$71.7967	$71.80	$71.80	$71.80
Purchase #2	$48.82	10.161%	$53.7806	$53.78	$53.80	$53.80
Purchase #3	$191.29	12.549%	$215.295	$215.30	$215.30	$215.30
Purchase #4	$233.85	9.429%	$255.8997	$255.90	$255.90	$255.90
Purchase #5	$98.31	8.141%	$106.3134	$106.31	$106.30	$106.30
Purchase #6	$51.28	11.358%	$57.1044	$57.10	$57.10	$57.10
Purchase #7	$242.50	6.263%	$257.6878	$257.69	$257.70	$257.70
7 purchase totals =	$933.38		$1,017.8776	$1,017.88	$1,017.90	$1,017.90