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	$107.65	7.761%	$116.0047	$116.00	$116.00	$116.00
Purchase #2	$239.54	11.238%	$266.4595	$266.46	$266.45	$266.50
Purchase #3	$139.37	13.485%	$158.164	$158.16	$158.15	$158.20
Purchase #4	$122.71	13.494%	$139.2685	$139.27	$139.25	$139.30
Purchase #5	$78.49	13.783%	$89.3083	$89.31	$89.30	$89.30
Purchase #6	$115.48	6.253%	$122.701	$122.70	$122.70	$122.70
Purchase #7	$39.78	7.643%	$42.8204	$42.82	$42.80	$42.80
7 purchase totals =	$843.02		$934.7264	$934.72	$934.65	$934.80