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	$210.46	6.222%	$223.5548	$223.55	$223.55	$223.60
Purchase #2	$144.91	10.742%	$160.4762	$160.48	$160.50	$160.50
Purchase #3	$30.52	3.530%	$31.5974	$31.60	$31.60	$31.60
Purchase #4	$233.31	4.612%	$244.0703	$244.07	$244.05	$244.10
Purchase #5	$203.28	4.299%	$212.019	$212.02	$212.00	$212.00
Purchase #6	$146.82	4.630%	$153.6178	$153.62	$153.60	$153.60
Purchase #7	$242.27	5.288%	$255.0812	$255.08	$255.10	$255.10
7 purchase totals =	$1,211.57		$1,280.4167	$1,280.42	$1,280.40	$1,280.50