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	$68.29	5.550%	$72.0801	$72.08	$72.10	$72.10
Purchase #2	$20.59	9.222%	$22.4888	$22.49	$22.50	$22.50
Purchase #3	$127.41	7.622%	$137.1212	$137.12	$137.10	$137.10
Purchase #4	$53.29	7.861%	$57.4791	$57.48	$57.50	$57.50
Purchase #5	$40.94	10.463%	$45.2236	$45.22	$45.20	$45.20
Purchase #6	$142.78	4.832%	$149.6791	$149.68	$149.70	$149.70
Purchase #7	$160.42	11.173%	$178.3437	$178.34	$178.35	$178.30
7 purchase totals =	$613.72		$662.4156	$662.41	$662.45	$662.40