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	$131.89	11.245%	$146.721	$146.72	$146.70	$146.70
Purchase #2	$173.86	12.787%	$196.0915	$196.09	$196.10	$196.10
Purchase #3	$125.49	4.612%	$131.2776	$131.28	$131.30	$131.30
Purchase #4	$29.84	4.634%	$31.2228	$31.22	$31.20	$31.20
Purchase #5	$74.34	3.837%	$77.1924	$77.19	$77.20	$77.20
Purchase #6	$44.99	4.853%	$47.1734	$47.17	$47.15	$47.20
Purchase #7	$216.66	10.198%	$238.755	$238.76	$238.75	$238.80
7 purchase totals =	$797.07		$868.4337	$868.43	$868.40	$868.50