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	$154.97	7.636%	$166.8035	$166.80	$166.80	$166.80
Purchase #2	$107.71	9.560%	$118.0071	$118.01	$118.00	$118.00
Purchase #3	$11.52	9.152%	$12.5743	$12.57	$12.55	$12.60
Purchase #4	$107.30	10.374%	$118.4313	$118.43	$118.45	$118.40
Purchase #5	$218.59	10.712%	$242.0054	$242.01	$242.00	$242.00
Purchase #6	$99.75	4.735%	$104.4732	$104.47	$104.45	$104.50
Purchase #7	$176.64	11.205%	$196.4325	$196.43	$196.45	$196.40
7 purchase totals =	$876.48		$958.7273	$958.72	$958.70	$958.70