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	$218.99	5.164%	$230.2986	$230.30	$230.30	$230.30
Purchase #2	$144.90	9.675%	$158.9191	$158.92	$158.90	$158.90
Purchase #3	$186.60	5.392%	$196.6615	$196.66	$196.65	$196.70
Purchase #4	$45.80	11.172%	$50.9168	$50.92	$50.90	$50.90
Purchase #5	$102.84	10.866%	$114.0146	$114.01	$114.00	$114.00
Purchase #6	$92.55	4.224%	$96.4593	$96.46	$96.45	$96.50
Purchase #7	$117.90	8.449%	$127.8614	$127.86	$127.85	$127.90
7 purchase totals =	$909.58		$975.1313	$975.13	$975.05	$975.20