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	$49.81	13.871%	$56.7191	$56.72	$56.70	$56.70
Purchase #2	$66.45	3.847%	$69.0063	$69.01	$69.00	$69.00
Purchase #3	$235.51	5.227%	$247.8201	$247.82	$247.80	$247.80
Purchase #4	$104.64	4.626%	$109.4806	$109.48	$109.50	$109.50
Purchase #5	$244.57	3.226%	$252.4598	$252.46	$252.45	$252.50
Purchase #6	$246.37	3.729%	$255.5571	$255.56	$255.55	$255.60
Purchase #7	$117.68	4.851%	$123.3887	$123.39	$123.40	$123.40
7 purchase totals =	$1,065.03		$1,114.4317	$1,114.44	$1,114.40	$1,114.50