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	$94.50	11.150%	$105.0368	$105.04	$105.05	$105.00
Purchase #2	$164.64	7.231%	$176.5451	$176.55	$176.55	$176.50
Purchase #3	$138.26	6.118%	$146.7187	$146.72	$146.70	$146.70
Purchase #4	$104.52	6.473%	$111.2856	$111.29	$111.30	$111.30
Purchase #5	$134.68	3.677%	$139.6322	$139.63	$139.65	$139.60
Purchase #6	$179.42	10.206%	$197.7316	$197.73	$197.75	$197.70
Purchase #7	$127.31	4.115%	$132.5488	$132.55	$132.55	$132.50
7 purchase totals =	$943.33		$1,009.4988	$1,009.51	$1,009.55	$1,009.30