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	$165.94	8.105%	$179.3894	$179.39	$179.40	$179.40
Purchase #2	$86.60	10.263%	$95.4878	$95.49	$95.50	$95.50
Purchase #3	$20.77	3.585%	$21.5146	$21.51	$21.50	$21.50
Purchase #4	$116.72	12.122%	$130.8688	$130.87	$130.85	$130.90
Purchase #5	$161.68	6.837%	$172.7341	$172.73	$172.75	$172.70
Purchase #6	$224.85	12.663%	$253.3228	$253.32	$253.30	$253.30
Purchase #7	$248.25	10.572%	$274.495	$274.50	$274.50	$274.50
7 purchase totals =	$1,024.81		$1,127.8125	$1,127.81	$1,127.80	$1,127.80