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	$117.79	12.429%	$132.4301	$132.43	$132.45	$132.40
Purchase #2	$142.92	8.470%	$155.0253	$155.03	$155.05	$155.00
Purchase #3	$217.40	11.837%	$243.1336	$243.13	$243.15	$243.10
Purchase #4	$114.86	11.319%	$127.861	$127.86	$127.85	$127.90
Purchase #5	$159.77	13.179%	$180.8261	$180.83	$180.85	$180.80
Purchase #6	$207.94	12.237%	$233.3856	$233.39	$233.40	$233.40
Purchase #7	$87.44	13.504%	$99.2479	$99.25	$99.25	$99.20
7 purchase totals =	$1,048.12		$1,171.9096	$1,171.92	$1,172.00	$1,171.80