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	$181.61	10.391%	$200.4811	$200.48	$200.50	$200.50
Purchase #2	$239.84	4.623%	$250.9278	$250.93	$250.95	$250.90
Purchase #3	$80.49	6.779%	$85.9464	$85.95	$85.95	$85.90
Purchase #4	$127.37	7.831%	$137.3443	$137.34	$137.35	$137.30
Purchase #5	$169.59	8.145%	$183.4031	$183.40	$183.40	$183.40
Purchase #6	$247.73	4.439%	$258.7267	$258.73	$258.75	$258.70
Purchase #7	$233.87	9.172%	$255.3206	$255.32	$255.30	$255.30
7 purchase totals =	$1,280.50		$1,372.1500	$1,372.15	$1,372.20	$1,372.00