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	$156.63	6.411%	$166.6715	$166.67	$166.65	$166.70
Purchase #2	$149.43	5.830%	$158.1418	$158.14	$158.15	$158.10
Purchase #3	$225.26	9.604%	$246.894	$246.89	$246.90	$246.90
Purchase #4	$223.70	3.234%	$230.9345	$230.93	$230.95	$230.90
Purchase #5	$113.36	11.596%	$126.5052	$126.51	$126.50	$126.50
Purchase #6	$24.35	4.737%	$25.5035	$25.50	$25.50	$25.50
Purchase #7	$59.31	9.456%	$64.9184	$64.92	$64.90	$64.90
7 purchase totals =	$952.04		$1,019.5689	$1,019.56	$1,019.55	$1,019.50