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	$137.70	5.196%	$144.8549	$144.85	$144.85	$144.90
Purchase #2	$46.71	8.392%	$50.6299	$50.63	$50.65	$50.60
Purchase #3	$221.71	11.435%	$247.0625	$247.06	$247.05	$247.10
Purchase #4	$221.39	13.131%	$250.4607	$250.46	$250.45	$250.50
Purchase #5	$17.30	11.313%	$19.2571	$19.26	$19.25	$19.30
Purchase #6	$51.34	5.284%	$54.0528	$54.05	$54.05	$54.10
Purchase #7	$233.32	3.859%	$242.3238	$242.32	$242.30	$242.30
7 purchase totals =	$929.47		$1,008.6417	$1,008.63	$1,008.60	$1,008.80