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	$116.84	8.852%	$127.1827	$127.18	$127.20	$127.20
Purchase #2	$175.64	5.741%	$185.7235	$185.72	$185.70	$185.70
Purchase #3	$177.98	11.840%	$199.0528	$199.05	$199.05	$199.10
Purchase #4	$113.60	8.595%	$123.3639	$123.36	$123.35	$123.40
Purchase #5	$35.88	3.302%	$37.0648	$37.06	$37.05	$37.10
Purchase #6	$71.81	8.665%	$78.0323	$78.03	$78.05	$78.00
Purchase #7	$203.37	11.235%	$226.2186	$226.22	$226.20	$226.20
7 purchase totals =	$895.12		$976.6386	$976.62	$976.60	$976.70