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	$221.41	11.484%	$246.8367	$246.84	$246.85	$246.80
Purchase #2	$133.89	11.621%	$149.4494	$149.45	$149.45	$149.40
Purchase #3	$165.86	4.243%	$172.8974	$172.90	$172.90	$172.90
Purchase #4	$250.69	13.635%	$284.8716	$284.87	$284.85	$284.90
Purchase #5	$23.28	9.388%	$25.4655	$25.47	$25.45	$25.50
Purchase #6	$131.44	8.265%	$142.3035	$142.30	$142.30	$142.30
Purchase #7	$138.95	5.447%	$146.5186	$146.52	$146.50	$146.50
7 purchase totals =	$1,065.52		$1,168.3427	$1,168.35	$1,168.30	$1,168.30