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	$116.41	9.749%	$127.7588	$127.76	$127.75	$127.80
Purchase #2	$37.84	9.731%	$41.5222	$41.52	$41.50	$41.50
Purchase #3	$65.99	9.437%	$72.2175	$72.22	$72.20	$72.20
Purchase #4	$150.88	4.174%	$157.1777	$157.18	$157.20	$157.20
Purchase #5	$126.88	9.516%	$138.9539	$138.95	$138.95	$139.00
Purchase #6	$48.46	13.366%	$54.9372	$54.94	$54.95	$54.90
Purchase #7	$54.38	11.449%	$60.606	$60.61	$60.60	$60.60
7 purchase totals =	$600.84		$653.1733	$653.18	$653.15	$653.20