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	$88.39	11.588%	$98.6326	$98.63	$98.65	$98.60
Purchase #2	$9.61	8.702%	$10.4463	$10.45	$10.45	$10.40
Purchase #3	$129.31	3.839%	$134.2742	$134.27	$134.25	$134.30
Purchase #4	$145.86	12.791%	$164.517	$164.52	$164.50	$164.50
Purchase #5	$117.37	9.374%	$128.3723	$128.37	$128.35	$128.40
Purchase #6	$52.26	6.372%	$55.59	$55.59	$55.60	$55.60
Purchase #7	$114.77	11.328%	$127.7711	$127.77	$127.75	$127.80
7 purchase totals =	$657.57		$719.6035	$719.60	$719.55	$719.60