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	$60.51	10.558%	$66.8986	$66.90	$66.90	$66.90
Purchase #2	$153.58	12.440%	$172.6854	$172.69	$172.70	$172.70
Purchase #3	$166.55	5.721%	$176.0783	$176.08	$176.10	$176.10
Purchase #4	$164.87	9.838%	$181.0899	$181.09	$181.10	$181.10
Purchase #5	$64.91	10.152%	$71.4997	$71.50	$71.50	$71.50
Purchase #6	$236.32	13.873%	$269.1047	$269.10	$269.10	$269.10
Purchase #7	$149.68	8.434%	$162.304	$162.30	$162.30	$162.30
7 purchase totals =	$996.42		$1,099.6606	$1,099.66	$1,099.70	$1,099.70