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	$172.61	11.723%	$192.8451	$192.85	$192.85	$192.80
Purchase #2	$137.62	12.724%	$155.1308	$155.13	$155.15	$155.10
Purchase #3	$122.53	4.415%	$127.9397	$127.94	$127.95	$127.90
Purchase #4	$45.92	9.477%	$50.2718	$50.27	$50.25	$50.30
Purchase #5	$89.52	5.777%	$94.6916	$94.69	$94.70	$94.70
Purchase #6	$227.79	3.364%	$235.4529	$235.45	$235.45	$235.50
Purchase #7	$172.75	7.374%	$185.4886	$185.49	$185.50	$185.50
7 purchase totals =	$968.74		$1,041.8205	$1,041.82	$1,041.85	$1,041.80