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	$100.89	10.111%	$111.091	$111.09	$111.10	$111.10
Purchase #2	$29.72	9.774%	$32.6248	$32.62	$32.60	$32.60
Purchase #3	$79.44	3.712%	$82.3888	$82.39	$82.40	$82.40
Purchase #4	$180.45	10.817%	$199.9693	$199.97	$199.95	$200.00
Purchase #5	$89.68	10.162%	$98.7933	$98.79	$98.80	$98.80
Purchase #6	$32.76	8.628%	$35.5865	$35.59	$35.60	$35.60
Purchase #7	$107.52	10.418%	$118.7214	$118.72	$118.70	$118.70
7 purchase totals =	$620.46		$679.1751	$679.17	$679.15	$679.20