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	$101.28	9.418%	$110.8186	$110.82	$110.80	$110.80
Purchase #2	$127.71	11.815%	$142.7989	$142.80	$142.80	$142.80
Purchase #3	$183.57	4.727%	$192.2474	$192.25	$192.25	$192.20
Purchase #4	$157.37	5.689%	$166.3228	$166.32	$166.30	$166.30
Purchase #5	$176.38	13.123%	$199.5263	$199.53	$199.55	$199.50
Purchase #6	$139.45	11.222%	$155.0991	$155.10	$155.10	$155.10
Purchase #7	$12.85	11.291%	$14.3009	$14.30	$14.30	$14.30
7 purchase totals =	$898.61		$981.1140	$981.12	$981.10	$981.00