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	$228.61	11.471%	$254.8339	$254.83	$254.85	$254.80
Purchase #2	$92.30	8.519%	$100.163	$100.16	$100.15	$100.20
Purchase #3	$13.97	8.102%	$15.1018	$15.10	$15.10	$15.10
Purchase #4	$105.76	5.572%	$111.6529	$111.65	$111.65	$111.70
Purchase #5	$192.64	8.238%	$208.5097	$208.51	$208.50	$208.50
Purchase #6	$30.51	8.718%	$33.1699	$33.17	$33.15	$33.20
Purchase #7	$139.99	13.756%	$159.247	$159.25	$159.25	$159.20
7 purchase totals =	$803.78		$882.6782	$882.67	$882.65	$882.70