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	$152.89	10.223%	$168.5199	$168.52	$168.50	$168.50
Purchase #2	$10.78	6.594%	$11.4908	$11.49	$11.50	$11.50
Purchase #3	$221.98	13.822%	$252.6621	$252.66	$252.65	$252.70
Purchase #4	$108.81	13.488%	$123.4863	$123.49	$123.50	$123.50
Purchase #5	$141.67	8.765%	$154.0874	$154.09	$154.10	$154.10
Purchase #6	$29.90	11.545%	$33.352	$33.35	$33.35	$33.40
Purchase #7	$152.42	8.341%	$165.1334	$165.13	$165.15	$165.10
7 purchase totals =	$818.45		$908.7319	$908.73	$908.75	$908.80