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	$66.81	8.702%	$72.6238	$72.62	$72.60	$72.60
Purchase #2	$162.34	4.803%	$170.1372	$170.14	$170.15	$170.10
Purchase #3	$108.65	6.685%	$115.9133	$115.91	$115.90	$115.90
Purchase #4	$208.72	10.325%	$230.2703	$230.27	$230.25	$230.30
Purchase #5	$101.89	9.194%	$111.2578	$111.26	$111.25	$111.30
Purchase #6	$190.57	8.592%	$206.9438	$206.94	$206.95	$206.90
Purchase #7	$250.31	13.733%	$284.6851	$284.69	$284.70	$284.70
7 purchase totals =	$1,089.29		$1,191.8313	$1,191.83	$1,191.80	$1,191.80