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	$221.90	9.461%	$242.894	$242.89	$242.90	$242.90
Purchase #2	$249.45	11.590%	$278.3613	$278.36	$278.35	$278.40
Purchase #3	$187.75	9.478%	$205.5449	$205.54	$205.55	$205.50
Purchase #4	$52.50	13.727%	$59.7067	$59.71	$59.70	$59.70
Purchase #5	$183.98	10.810%	$203.8682	$203.87	$203.85	$203.90
Purchase #6	$132.66	4.654%	$138.834	$138.83	$138.85	$138.80
Purchase #7	$95.26	5.560%	$100.5565	$100.56	$100.55	$100.60
7 purchase totals =	$1,123.50		$1,229.7656	$1,229.76	$1,229.75	$1,229.80