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	$14.59	3.795%	$15.1437	$15.14	$15.15	$15.10
Purchase #2	$20.67	6.420%	$21.997	$22.00	$22.00	$22.00
Purchase #3	$72.95	8.293%	$78.9997	$79.00	$79.00	$79.00
Purchase #4	$161.79	4.370%	$168.8602	$168.86	$168.85	$168.90
Purchase #5	$89.49	13.611%	$101.6705	$101.67	$101.65	$101.70
Purchase #6	$104.73	7.762%	$112.8591	$112.86	$112.85	$112.90
Purchase #7	$177.64	10.821%	$196.8624	$196.86	$196.85	$196.90
7 purchase totals =	$641.86		$696.3926	$696.39	$696.35	$696.50