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	$184.42	9.151%	$201.2963	$201.30	$201.30	$201.30
Purchase #2	$116.98	8.785%	$127.2567	$127.26	$127.25	$127.30
Purchase #3	$187.89	9.335%	$205.4295	$205.43	$205.45	$205.40
Purchase #4	$152.69	9.706%	$167.5101	$167.51	$167.50	$167.50
Purchase #5	$46.72	7.308%	$50.1343	$50.13	$50.15	$50.10
Purchase #6	$130.39	12.429%	$146.5962	$146.60	$146.60	$146.60
Purchase #7	$74.46	12.543%	$83.7995	$83.80	$83.80	$83.80
7 purchase totals =	$893.55		$982.0226	$982.03	$982.05	$982.00