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	$177.54	10.449%	$196.0912	$196.09	$196.10	$196.10
Purchase #2	$202.91	5.673%	$214.4211	$214.42	$214.40	$214.40
Purchase #3	$113.28	11.381%	$126.1724	$126.17	$126.15	$126.20
Purchase #4	$144.68	6.253%	$153.7268	$153.73	$153.75	$153.70
Purchase #5	$108.83	13.578%	$123.6069	$123.61	$123.60	$123.60
Purchase #6	$209.45	7.637%	$225.4457	$225.45	$225.45	$225.40
Purchase #7	$49.87	12.424%	$56.0658	$56.07	$56.05	$56.10
7 purchase totals =	$1,006.56		$1,095.5299	$1,095.54	$1,095.50	$1,095.50