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	$12.28	4.729%	$12.8607	$12.86	$12.85	$12.90
Purchase #2	$90.53	4.627%	$94.7188	$94.72	$94.70	$94.70
Purchase #3	$116.46	4.856%	$122.1153	$122.12	$122.10	$122.10
Purchase #4	$230.78	10.362%	$254.6934	$254.69	$254.70	$254.70
Purchase #5	$102.74	8.293%	$111.2602	$111.26	$111.25	$111.30
Purchase #6	$113.31	13.236%	$128.3077	$128.31	$128.30	$128.30
Purchase #7	$46.57	3.520%	$48.2093	$48.21	$48.20	$48.20
7 purchase totals =	$712.67		$772.1654	$772.17	$772.10	$772.20