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	$49.67	10.508%	$54.8893	$54.89	$54.90	$54.90
Purchase #2	$233.79	10.552%	$258.4595	$258.46	$258.45	$258.50
Purchase #3	$94.67	5.716%	$100.0813	$100.08	$100.10	$100.10
Purchase #4	$11.55	7.679%	$12.4369	$12.44	$12.45	$12.40
Purchase #5	$132.92	13.242%	$150.5213	$150.52	$150.50	$150.50
Purchase #6	$178.72	13.499%	$202.8454	$202.85	$202.85	$202.80
Purchase #7	$236.69	4.807%	$248.0677	$248.07	$248.05	$248.10
7 purchase totals =	$938.01		$1,027.3014	$1,027.31	$1,027.30	$1,027.30