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	$99.84	11.569%	$111.3905	$111.39	$111.40	$111.40
Purchase #2	$235.91	4.797%	$247.2266	$247.23	$247.25	$247.20
Purchase #3	$103.60	6.138%	$109.959	$109.96	$109.95	$110.00
Purchase #4	$168.52	13.388%	$191.0815	$191.08	$191.10	$191.10
Purchase #5	$48.96	11.111%	$54.3999	$54.40	$54.40	$54.40
Purchase #6	$105.52	10.306%	$116.3949	$116.39	$116.40	$116.40
Purchase #7	$135.80	13.212%	$153.7419	$153.74	$153.75	$153.70
7 purchase totals =	$898.15		$984.1943	$984.19	$984.25	$984.20