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	$239.92	6.505%	$255.5268	$255.53	$255.55	$255.50
Purchase #2	$153.33	13.547%	$174.1016	$174.10	$174.10	$174.10
Purchase #3	$245.44	12.240%	$275.4819	$275.48	$275.50	$275.50
Purchase #4	$103.53	4.368%	$108.0522	$108.05	$108.05	$108.10
Purchase #5	$181.42	8.192%	$196.2819	$196.28	$196.30	$196.30
Purchase #6	$210.58	3.380%	$217.6976	$217.70	$217.70	$217.70
Purchase #7	$153.42	8.510%	$166.476	$166.48	$166.50	$166.50
7 purchase totals =	$1,287.64		$1,393.6180	$1,393.62	$1,393.70	$1,393.70