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	$107.78	3.528%	$111.5825	$111.58	$111.60	$111.60
Purchase #2	$195.48	8.179%	$211.4683	$211.47	$211.45	$211.50
Purchase #3	$66.68	6.347%	$70.9122	$70.91	$70.90	$70.90
Purchase #4	$78.65	13.526%	$89.2882	$89.29	$89.30	$89.30
Purchase #5	$107.75	6.849%	$115.1298	$115.13	$115.15	$115.10
Purchase #6	$33.46	5.397%	$35.2658	$35.27	$35.25	$35.30
Purchase #7	$97.97	5.193%	$103.0576	$103.06	$103.05	$103.10
7 purchase totals =	$687.77		$736.7044	$736.71	$736.70	$736.80