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	$237.33	6.395%	$252.5073	$252.51	$252.50	$252.50
Purchase #2	$74.89	4.319%	$78.1245	$78.12	$78.10	$78.10
Purchase #3	$156.36	6.360%	$166.3045	$166.30	$166.30	$166.30
Purchase #4	$20.25	5.848%	$21.4342	$21.43	$21.45	$21.40
Purchase #5	$39.81	3.638%	$41.2583	$41.26	$41.25	$41.30
Purchase #6	$53.73	12.163%	$60.2652	$60.27	$60.25	$60.30
Purchase #7	$106.38	3.109%	$109.6874	$109.69	$109.70	$109.70
7 purchase totals =	$688.75		$729.5814	$729.58	$729.55	$729.60