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	$176.48	13.194%	$199.7648	$199.76	$199.75	$199.80
Purchase #2	$138.52	3.852%	$143.8558	$143.86	$143.85	$143.90
Purchase #3	$139.35	13.508%	$158.1734	$158.17	$158.15	$158.20
Purchase #4	$52.54	8.700%	$57.111	$57.11	$57.10	$57.10
Purchase #5	$187.85	13.633%	$213.4596	$213.46	$213.45	$213.50
Purchase #6	$162.42	6.125%	$172.3682	$172.37	$172.35	$172.40
Purchase #7	$132.66	9.780%	$145.6341	$145.63	$145.65	$145.60
7 purchase totals =	$989.82		$1,090.3669	$1,090.36	$1,090.30	$1,090.50