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	$21.35	3.109%	$22.0138	$22.01	$22.00	$22.00
Purchase #2	$11.42	3.575%	$11.8283	$11.83	$11.85	$11.80
Purchase #3	$144.64	5.406%	$152.4592	$152.46	$152.45	$152.50
Purchase #4	$208.37	13.433%	$236.3603	$236.36	$236.35	$236.40
Purchase #5	$114.68	7.696%	$123.5058	$123.51	$123.50	$123.50
Purchase #6	$69.26	4.599%	$72.4453	$72.45	$72.45	$72.40
Purchase #7	$118.91	11.481%	$132.5621	$132.56	$132.55	$132.60
7 purchase totals =	$688.63		$751.1748	$751.18	$751.15	$751.20