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	$157.29	4.537%	$164.4262	$164.43	$164.45	$164.40
Purchase #2	$106.30	7.468%	$114.2385	$114.24	$114.25	$114.20
Purchase #3	$198.75	12.174%	$222.9458	$222.95	$222.95	$222.90
Purchase #4	$226.62	6.480%	$241.305	$241.31	$241.30	$241.30
Purchase #5	$46.77	3.759%	$48.5281	$48.53	$48.55	$48.50
Purchase #6	$99.70	6.834%	$106.5135	$106.51	$106.50	$106.50
Purchase #7	$40.47	5.465%	$42.6817	$42.68	$42.70	$42.70
7 purchase totals =	$875.90		$940.6388	$940.65	$940.70	$940.50