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	$193.35	8.348%	$209.4909	$209.49	$209.50	$209.50
Purchase #2	$28.28	4.772%	$29.6295	$29.63	$29.65	$29.60
Purchase #3	$184.40	6.403%	$196.2071	$196.21	$196.20	$196.20
Purchase #4	$114.42	11.583%	$127.6733	$127.67	$127.65	$127.70
Purchase #5	$74.65	13.282%	$84.565	$84.57	$84.55	$84.60
Purchase #6	$181.31	3.839%	$188.2705	$188.27	$188.25	$188.30
Purchase #7	$100.25	11.159%	$111.4369	$111.44	$111.45	$111.40
7 purchase totals =	$876.66		$947.2732	$947.28	$947.25	$947.30