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	$71.53	9.210%	$78.1179	$78.12	$78.10	$78.10
Purchase #2	$31.75	8.606%	$34.4824	$34.48	$34.50	$34.50
Purchase #3	$101.45	10.326%	$111.9257	$111.93	$111.95	$111.90
Purchase #4	$157.70	9.651%	$172.9196	$172.92	$172.90	$172.90
Purchase #5	$226.58	5.493%	$239.026	$239.03	$239.05	$239.00
Purchase #6	$64.88	10.607%	$71.7618	$71.76	$71.75	$71.80
Purchase #7	$150.40	5.858%	$159.2104	$159.21	$159.20	$159.20
7 purchase totals =	$804.29		$867.4438	$867.45	$867.45	$867.40