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	$223.26	4.569%	$233.4607	$233.46	$233.45	$233.50
Purchase #2	$40.76	7.717%	$43.9054	$43.91	$43.90	$43.90
Purchase #3	$38.94	13.694%	$44.2724	$44.27	$44.25	$44.30
Purchase #4	$235.72	12.314%	$264.7466	$264.75	$264.75	$264.70
Purchase #5	$163.57	13.235%	$185.2185	$185.22	$185.20	$185.20
Purchase #6	$183.78	8.150%	$198.7581	$198.76	$198.75	$198.80
Purchase #7	$120.41	11.365%	$134.0946	$134.09	$134.10	$134.10
7 purchase totals =	$1,006.44		$1,104.4563	$1,104.46	$1,104.40	$1,104.50