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	$112.77	13.313%	$127.7831	$127.78	$127.80	$127.80
Purchase #2	$17.95	8.328%	$19.4449	$19.44	$19.45	$19.40
Purchase #3	$105.70	8.836%	$115.0397	$115.04	$115.05	$115.00
Purchase #4	$107.69	3.750%	$111.7284	$111.73	$111.75	$111.70
Purchase #5	$180.52	8.166%	$195.2613	$195.26	$195.25	$195.30
Purchase #6	$187.82	4.769%	$196.7771	$196.78	$196.80	$196.80
Purchase #7	$47.25	7.447%	$50.7687	$50.77	$50.75	$50.80
7 purchase totals =	$759.70		$816.8032	$816.80	$816.85	$816.80