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	$216.92	4.487%	$226.6532	$226.65	$226.65	$226.70
Purchase #2	$239.33	7.256%	$256.6958	$256.70	$256.70	$256.70
Purchase #3	$68.39	8.853%	$74.4446	$74.44	$74.45	$74.40
Purchase #4	$48.87	11.566%	$54.5223	$54.52	$54.50	$54.50
Purchase #5	$204.78	9.274%	$223.7713	$223.77	$223.75	$223.80
Purchase #6	$127.46	9.128%	$139.0945	$139.09	$139.10	$139.10
Purchase #7	$40.43	4.611%	$42.2942	$42.29	$42.30	$42.30
7 purchase totals =	$946.18		$1,017.4759	$1,017.46	$1,017.45	$1,017.50