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	$165.29	9.298%	$180.6587	$180.66	$180.65	$180.70
Purchase #2	$70.35	11.709%	$78.5873	$78.59	$78.60	$78.60
Purchase #3	$47.93	4.404%	$50.0408	$50.04	$50.05	$50.00
Purchase #4	$5.77	11.406%	$6.4281	$6.43	$6.45	$6.40
Purchase #5	$117.32	9.442%	$128.3974	$128.40	$128.40	$128.40
Purchase #6	$14.55	12.617%	$16.3858	$16.39	$16.40	$16.40
Purchase #7	$79.42	13.483%	$90.1282	$90.13	$90.15	$90.10
7 purchase totals =	$500.63		$550.6263	$550.64	$550.70	$550.60