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	$176.28	4.845%	$184.8208	$184.82	$184.80	$184.80
Purchase #2	$193.86	5.788%	$205.0806	$205.08	$205.10	$205.10
Purchase #3	$96.38	7.190%	$103.3097	$103.31	$103.30	$103.30
Purchase #4	$230.31	12.552%	$259.2185	$259.22	$259.20	$259.20
Purchase #5	$138.46	4.222%	$144.3058	$144.31	$144.30	$144.30
Purchase #6	$110.81	11.549%	$123.6074	$123.61	$123.60	$123.60
Purchase #7	$226.58	12.328%	$254.5128	$254.51	$254.50	$254.50
7 purchase totals =	$1,172.68		$1,274.8556	$1,274.86	$1,274.80	$1,274.80