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	$192.46	11.215%	$214.0444	$214.04	$214.05	$214.00
Purchase #2	$186.74	7.318%	$200.4056	$200.41	$200.40	$200.40
Purchase #3	$248.56	4.252%	$259.1288	$259.13	$259.15	$259.10
Purchase #4	$117.81	12.315%	$132.3183	$132.32	$132.30	$132.30
Purchase #5	$76.97	12.839%	$86.8522	$86.85	$86.85	$86.90
Purchase #6	$19.54	9.848%	$21.4643	$21.46	$21.45	$21.50
Purchase #7	$78.78	11.768%	$88.0508	$88.05	$88.05	$88.10
7 purchase totals =	$920.86		$1,002.2644	$1,002.26	$1,002.25	$1,002.30