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	$105.88	10.291%	$116.7761	$116.78	$116.80	$116.80
Purchase #2	$56.50	4.449%	$59.0137	$59.01	$59.00	$59.00
Purchase #3	$159.42	8.422%	$172.8464	$172.85	$172.85	$172.80
Purchase #4	$223.74	3.467%	$231.4971	$231.50	$231.50	$231.50
Purchase #5	$33.89	4.485%	$35.41	$35.41	$35.40	$35.40
Purchase #6	$221.76	3.269%	$229.0093	$229.01	$229.00	$229.00
Purchase #7	$15.70	9.708%	$17.2242	$17.22	$17.20	$17.20
7 purchase totals =	$816.89		$861.7768	$861.78	$861.75	$861.70