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	$102.50	9.113%	$111.8408	$111.84	$111.85	$111.80
Purchase #2	$50.78	10.477%	$56.1002	$56.10	$56.10	$56.10
Purchase #3	$200.37	11.717%	$223.8474	$223.85	$223.85	$223.80
Purchase #4	$185.79	12.719%	$209.4206	$209.42	$209.40	$209.40
Purchase #5	$78.75	11.483%	$87.7929	$87.79	$87.80	$87.80
Purchase #6	$143.76	5.377%	$151.49	$151.49	$151.50	$151.50
Purchase #7	$21.30	3.811%	$22.1117	$22.11	$22.10	$22.10
7 purchase totals =	$783.25		$862.6036	$862.60	$862.60	$862.50