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	$140.61	9.653%	$154.1831	$154.18	$154.20	$154.20
Purchase #2	$166.76	3.146%	$172.0063	$172.01	$172.00	$172.00
Purchase #3	$176.95	3.161%	$182.5434	$182.54	$182.55	$182.50
Purchase #4	$114.55	11.483%	$127.7038	$127.70	$127.70	$127.70
Purchase #5	$58.45	13.328%	$66.2402	$66.24	$66.25	$66.20
Purchase #6	$152.96	7.767%	$164.8404	$164.84	$164.85	$164.80
Purchase #7	$16.57	8.687%	$18.0094	$18.01	$18.00	$18.00
7 purchase totals =	$826.85		$885.5266	$885.52	$885.55	$885.40