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	$218.60	12.517%	$245.9622	$245.96	$245.95	$246.00
Purchase #2	$220.71	5.831%	$233.5796	$233.58	$233.60	$233.60
Purchase #3	$189.27	6.359%	$201.3057	$201.31	$201.30	$201.30
Purchase #4	$132.51	13.479%	$150.371	$150.37	$150.35	$150.40
Purchase #5	$117.27	8.626%	$127.3857	$127.39	$127.40	$127.40
Purchase #6	$49.91	11.345%	$55.5723	$55.57	$55.55	$55.60
Purchase #7	$61.70	7.112%	$66.0881	$66.09	$66.10	$66.10
7 purchase totals =	$989.97		$1,080.2646	$1,080.27	$1,080.25	$1,080.40