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	$62.38	13.252%	$70.6466	$70.65	$70.65	$70.60
Purchase #2	$80.96	10.288%	$89.2892	$89.29	$89.30	$89.30
Purchase #3	$18.57	11.358%	$20.6792	$20.68	$20.70	$20.70
Purchase #4	$12.85	13.585%	$14.5957	$14.60	$14.60	$14.60
Purchase #5	$82.98	10.183%	$91.4299	$91.43	$91.45	$91.40
Purchase #6	$18.62	6.380%	$19.808	$19.81	$19.80	$19.80
Purchase #7	$56.84	10.304%	$62.6968	$62.70	$62.70	$62.70
7 purchase totals =	$333.20		$369.1454	$369.16	$369.20	$369.10