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	$88.49	13.659%	$100.5768	$100.58	$100.60	$100.60
Purchase #2	$152.36	9.747%	$167.2105	$167.21	$167.20	$167.20
Purchase #3	$46.53	5.366%	$49.0268	$49.03	$49.05	$49.00
Purchase #4	$9.86	6.160%	$10.4674	$10.47	$10.45	$10.50
Purchase #5	$173.61	9.524%	$190.1446	$190.14	$190.15	$190.10
Purchase #6	$34.83	10.436%	$38.4649	$38.46	$38.45	$38.50
Purchase #7	$137.87	13.261%	$156.1529	$156.15	$156.15	$156.20
7 purchase totals =	$643.55		$712.0439	$712.04	$712.05	$712.10