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	$181.52	6.675%	$193.6365	$193.64	$193.65	$193.60
Purchase #2	$91.63	4.131%	$95.4152	$95.42	$95.40	$95.40
Purchase #3	$241.91	4.640%	$253.1346	$253.13	$253.15	$253.10
Purchase #4	$124.28	7.685%	$133.8309	$133.83	$133.85	$133.80
Purchase #5	$186.51	6.233%	$198.1352	$198.14	$198.15	$198.10
Purchase #6	$132.39	5.476%	$139.6397	$139.64	$139.65	$139.60
Purchase #7	$171.32	6.682%	$182.7676	$182.77	$182.75	$182.80
7 purchase totals =	$1,129.56		$1,196.5597	$1,196.57	$1,196.60	$1,196.40