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	$170.90	3.305%	$176.5482	$176.55	$176.55	$176.50
Purchase #2	$164.25	5.286%	$172.9323	$172.93	$172.95	$172.90
Purchase #3	$117.49	8.710%	$127.7234	$127.72	$127.70	$127.70
Purchase #4	$171.54	11.107%	$190.5929	$190.59	$190.60	$190.60
Purchase #5	$100.51	3.623%	$104.1515	$104.15	$104.15	$104.20
Purchase #6	$244.30	6.545%	$260.2894	$260.29	$260.30	$260.30
Purchase #7	$79.76	5.632%	$84.2521	$84.25	$84.25	$84.30
7 purchase totals =	$1,048.75		$1,116.4898	$1,116.48	$1,116.50	$1,116.50