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	$222.40	11.720%	$248.4653	$248.47	$248.45	$248.50
Purchase #2	$28.95	12.623%	$32.6044	$32.60	$32.60	$32.60
Purchase #3	$78.47	13.536%	$89.0917	$89.09	$89.10	$89.10
Purchase #4	$41.32	12.311%	$46.4069	$46.41	$46.40	$46.40
Purchase #5	$103.92	7.507%	$111.7213	$111.72	$111.70	$111.70
Purchase #6	$212.29	12.426%	$238.6692	$238.67	$238.65	$238.70
Purchase #7	$210.78	7.559%	$226.7129	$226.71	$226.70	$226.70
7 purchase totals =	$898.13		$993.6717	$993.67	$993.60	$993.70