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	$208.54	10.366%	$230.1573	$230.16	$230.15	$230.20
Purchase #2	$107.39	10.836%	$119.0268	$119.03	$119.05	$119.00
Purchase #3	$11.26	10.650%	$12.4592	$12.46	$12.45	$12.50
Purchase #4	$79.67	12.395%	$89.5451	$89.55	$89.55	$89.50
Purchase #5	$239.93	11.722%	$268.0546	$268.05	$268.05	$268.10
Purchase #6	$76.90	11.258%	$85.5574	$85.56	$85.55	$85.60
Purchase #7	$43.62	11.381%	$48.5844	$48.58	$48.60	$48.60
7 purchase totals =	$767.31		$853.3848	$853.39	$853.40	$853.50