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	$69.38	9.102%	$75.695	$75.70	$75.70	$75.70
Purchase #2	$112.54	5.496%	$118.7252	$118.73	$118.75	$118.70
Purchase #3	$169.56	3.471%	$175.4454	$175.45	$175.45	$175.40
Purchase #4	$174.91	13.826%	$199.0931	$199.09	$199.10	$199.10
Purchase #5	$40.43	6.842%	$43.1962	$43.20	$43.20	$43.20
Purchase #6	$185.95	5.550%	$196.2702	$196.27	$196.25	$196.30
Purchase #7	$102.42	8.447%	$111.0714	$111.07	$111.05	$111.10
7 purchase totals =	$855.19		$919.4965	$919.51	$919.50	$919.50