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	$152.67	9.665%	$167.4256	$167.43	$167.45	$167.40
Purchase #2	$98.58	13.237%	$111.629	$111.63	$111.65	$111.60
Purchase #3	$155.93	13.395%	$176.8168	$176.82	$176.80	$176.80
Purchase #4	$131.42	5.306%	$138.3931	$138.39	$138.40	$138.40
Purchase #5	$79.45	4.449%	$82.9847	$82.98	$83.00	$83.00
Purchase #6	$125.64	10.321%	$138.6073	$138.61	$138.60	$138.60
Purchase #7	$150.45	3.779%	$156.1355	$156.14	$156.15	$156.10
7 purchase totals =	$894.14		$971.9920	$972.00	$972.05	$971.90