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	$166.97	5.574%	$176.2769	$176.28	$176.30	$176.30
Purchase #2	$240.29	7.577%	$258.4968	$258.50	$258.50	$258.50
Purchase #3	$113.93	11.490%	$127.0206	$127.02	$127.00	$127.00
Purchase #4	$127.73	9.448%	$139.7979	$139.80	$139.80	$139.80
Purchase #5	$140.86	12.618%	$158.6337	$158.63	$158.65	$158.60
Purchase #6	$138.46	10.415%	$152.8806	$152.88	$152.90	$152.90
Purchase #7	$41.26	7.397%	$44.312	$44.31	$44.30	$44.30
7 purchase totals =	$969.50		$1,057.4185	$1,057.42	$1,057.45	$1,057.40