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	$217.76	7.195%	$233.4278	$233.43	$233.45	$233.40
Purchase #2	$98.67	13.221%	$111.7152	$111.72	$111.70	$111.70
Purchase #3	$88.75	12.249%	$99.621	$99.62	$99.60	$99.60
Purchase #4	$150.43	12.107%	$168.6426	$168.64	$168.65	$168.60
Purchase #5	$161.39	10.191%	$177.8373	$177.84	$177.85	$177.80
Purchase #6	$151.67	9.800%	$166.5337	$166.53	$166.55	$166.50
Purchase #7	$56.80	6.532%	$60.5102	$60.51	$60.50	$60.50
7 purchase totals =	$925.47		$1,018.2878	$1,018.29	$1,018.30	$1,018.10