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	$190.82	13.723%	$217.0062	$217.01	$217.00	$217.00
Purchase #2	$25.65	5.777%	$27.1318	$27.13	$27.15	$27.10
Purchase #3	$248.87	7.328%	$267.1072	$267.11	$267.10	$267.10
Purchase #4	$17.59	5.541%	$18.5647	$18.56	$18.55	$18.60
Purchase #5	$120.75	8.564%	$131.091	$131.09	$131.10	$131.10
Purchase #6	$106.53	12.111%	$119.4318	$119.43	$119.45	$119.40
Purchase #7	$131.82	12.718%	$148.5849	$148.58	$148.60	$148.60
7 purchase totals =	$842.03		$928.9176	$928.91	$928.95	$928.90