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	$95.51	5.615%	$100.8729	$100.87	$100.85	$100.90
Purchase #2	$214.27	12.726%	$241.538	$241.54	$241.55	$241.50
Purchase #3	$137.55	9.687%	$150.8745	$150.87	$150.85	$150.90
Purchase #4	$53.70	13.300%	$60.8421	$60.84	$60.85	$60.80
Purchase #5	$134.54	13.779%	$153.0783	$153.08	$153.10	$153.10
Purchase #6	$143.96	9.798%	$158.0652	$158.07	$158.05	$158.10
Purchase #7	$248.77	11.871%	$278.3015	$278.30	$278.30	$278.30
7 purchase totals =	$1,028.30		$1,143.5725	$1,143.57	$1,143.55	$1,143.60