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	$234.58	8.658%	$254.8899	$254.89	$254.90	$254.90
Purchase #2	$82.78	9.491%	$90.6366	$90.64	$90.65	$90.60
Purchase #3	$91.67	9.325%	$100.2182	$100.22	$100.20	$100.20
Purchase #4	$74.38	11.140%	$82.6659	$82.67	$82.65	$82.70
Purchase #5	$126.89	11.196%	$141.0966	$141.10	$141.10	$141.10
Purchase #6	$135.72	11.493%	$151.3183	$151.32	$151.30	$151.30
Purchase #7	$58.37	11.202%	$64.9086	$64.91	$64.90	$64.90
7 purchase totals =	$804.39		$885.7341	$885.75	$885.70	$885.70