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	$139.37	3.645%	$144.45	$144.45	$144.45	$144.50
Purchase #2	$185.26	12.675%	$208.7417	$208.74	$208.75	$208.70
Purchase #3	$195.74	13.758%	$222.6699	$222.67	$222.65	$222.70
Purchase #4	$97.94	13.726%	$111.3832	$111.38	$111.40	$111.40
Purchase #5	$137.58	9.598%	$150.7849	$150.78	$150.80	$150.80
Purchase #6	$115.67	5.559%	$122.1001	$122.10	$122.10	$122.10
Purchase #7	$202.77	10.637%	$224.3386	$224.34	$224.35	$224.30
7 purchase totals =	$1,074.33		$1,184.4684	$1,184.46	$1,184.50	$1,184.50