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	$213.40	3.375%	$220.6023	$220.60	$220.60	$220.60
Purchase #2	$234.97	13.302%	$266.2257	$266.23	$266.25	$266.20
Purchase #3	$152.97	13.170%	$173.1161	$173.12	$173.10	$173.10
Purchase #4	$45.81	13.601%	$52.0406	$52.04	$52.05	$52.00
Purchase #5	$106.95	8.469%	$116.0076	$116.01	$116.00	$116.00
Purchase #6	$100.93	10.110%	$111.134	$111.13	$111.15	$111.10
Purchase #7	$197.80	13.127%	$223.7652	$223.77	$223.75	$223.80
7 purchase totals =	$1,052.83		$1,162.8915	$1,162.90	$1,162.90	$1,162.80