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	$61.86	4.719%	$64.7792	$64.78	$64.80	$64.80
Purchase #2	$41.49	13.390%	$47.0455	$47.05	$47.05	$47.00
Purchase #3	$75.88	3.692%	$78.6815	$78.68	$78.70	$78.70
Purchase #4	$118.52	13.814%	$134.8924	$134.89	$134.90	$134.90
Purchase #5	$130.73	7.803%	$140.9309	$140.93	$140.95	$140.90
Purchase #6	$192.25	10.340%	$212.1287	$212.13	$212.15	$212.10
Purchase #7	$153.30	8.189%	$165.8537	$165.85	$165.85	$165.90
7 purchase totals =	$774.03		$844.3119	$844.31	$844.40	$844.30