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	$77.33	8.658%	$84.0252	$84.03	$84.05	$84.00
Purchase #2	$133.72	6.575%	$142.5121	$142.51	$142.50	$142.50
Purchase #3	$218.69	5.439%	$230.5845	$230.58	$230.60	$230.60
Purchase #4	$87.75	3.505%	$90.8256	$90.83	$90.85	$90.80
Purchase #5	$215.66	12.395%	$242.3911	$242.39	$242.40	$242.40
Purchase #6	$134.30	11.182%	$149.3174	$149.32	$149.30	$149.30
Purchase #7	$83.55	3.131%	$86.166	$86.17	$86.15	$86.20
7 purchase totals =	$951.00		$1,025.8219	$1,025.83	$1,025.85	$1,025.80