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	$54.31	8.733%	$59.0529	$59.05	$59.05	$59.10
Purchase #2	$229.99	11.234%	$255.8271	$255.83	$255.85	$255.80
Purchase #3	$119.77	13.694%	$136.1713	$136.17	$136.15	$136.20
Purchase #4	$137.31	11.586%	$153.2187	$153.22	$153.20	$153.20
Purchase #5	$122.58	7.640%	$131.9451	$131.95	$131.95	$131.90
Purchase #6	$228.41	6.155%	$242.4686	$242.47	$242.45	$242.50
Purchase #7	$145.91	6.252%	$155.0323	$155.03	$155.05	$155.00
7 purchase totals =	$1,038.28		$1,133.7160	$1,133.72	$1,133.70	$1,133.70