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	$165.92	10.346%	$183.0861	$183.09	$183.10	$183.10
Purchase #2	$222.64	13.854%	$253.4845	$253.48	$253.50	$253.50
Purchase #3	$83.72	7.379%	$89.8977	$89.90	$89.90	$89.90
Purchase #4	$48.90	9.463%	$53.5274	$53.53	$53.55	$53.50
Purchase #5	$87.83	13.229%	$99.449	$99.45	$99.45	$99.40
Purchase #6	$119.43	5.237%	$125.6845	$125.68	$125.70	$125.70
Purchase #7	$121.50	9.275%	$132.7691	$132.77	$132.75	$132.80
7 purchase totals =	$849.94		$937.8983	$937.90	$937.95	$937.90