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	$150.28	10.264%	$165.7047	$165.70	$165.70	$165.70
Purchase #2	$134.95	7.191%	$144.6543	$144.65	$144.65	$144.70
Purchase #3	$120.29	9.734%	$131.999	$132.00	$132.00	$132.00
Purchase #4	$142.52	11.115%	$158.3611	$158.36	$158.35	$158.40
Purchase #5	$182.31	4.354%	$190.2478	$190.25	$190.25	$190.20
Purchase #6	$137.78	10.405%	$152.116	$152.12	$152.10	$152.10
Purchase #7	$127.50	9.198%	$139.2275	$139.23	$139.25	$139.20
7 purchase totals =	$995.63		$1,082.3104	$1,082.31	$1,082.30	$1,082.30