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	$143.58	10.542%	$158.7162	$158.72	$158.70	$158.70
Purchase #2	$96.49	13.269%	$109.2933	$109.29	$109.30	$109.30
Purchase #3	$171.34	3.130%	$176.7029	$176.70	$176.70	$176.70
Purchase #4	$151.42	13.765%	$172.263	$172.26	$172.25	$172.30
Purchase #5	$219.48	7.566%	$236.0859	$236.09	$236.10	$236.10
Purchase #6	$83.26	5.765%	$88.0599	$88.06	$88.05	$88.10
Purchase #7	$52.83	12.246%	$59.2996	$59.30	$59.30	$59.30
7 purchase totals =	$918.40		$1,000.4208	$1,000.42	$1,000.40	$1,000.50