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	$112.64	8.581%	$122.3056	$122.31	$122.30	$122.30
Purchase #2	$87.92	13.598%	$99.8754	$99.88	$99.90	$99.90
Purchase #3	$26.51	12.245%	$29.7561	$29.76	$29.75	$29.80
Purchase #4	$14.59	3.274%	$15.0677	$15.07	$15.05	$15.10
Purchase #5	$127.43	13.694%	$144.8803	$144.88	$144.90	$144.90
Purchase #6	$94.31	9.743%	$103.4986	$103.50	$103.50	$103.50
Purchase #7	$204.61	4.400%	$213.6128	$213.61	$213.60	$213.60
7 purchase totals =	$668.01		$728.9965	$729.01	$729.00	$729.10