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	$230.81	10.262%	$254.4957	$254.50	$254.50	$254.50
Purchase #2	$211.79	10.762%	$234.5828	$234.58	$234.60	$234.60
Purchase #3	$37.93	10.872%	$42.0537	$42.05	$42.05	$42.10
Purchase #4	$181.31	8.537%	$196.7884	$196.79	$196.80	$196.80
Purchase #5	$40.35	13.589%	$45.8332	$45.83	$45.85	$45.80
Purchase #6	$233.49	10.717%	$258.5131	$258.51	$258.50	$258.50
Purchase #7	$45.77	11.763%	$51.1539	$51.15	$51.15	$51.20
7 purchase totals =	$981.45		$1,083.4208	$1,083.41	$1,083.45	$1,083.50