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	$103.55	10.212%	$114.1245	$114.12	$114.10	$114.10
Purchase #2	$111.35	13.673%	$126.5749	$126.57	$126.55	$126.60
Purchase #3	$208.66	4.275%	$217.5802	$217.58	$217.60	$217.60
Purchase #4	$157.57	9.489%	$172.5218	$172.52	$172.50	$172.50
Purchase #5	$115.54	12.373%	$129.8358	$129.84	$129.85	$129.80
Purchase #6	$37.90	13.756%	$43.1135	$43.11	$43.10	$43.10
Purchase #7	$185.96	10.675%	$205.8112	$205.81	$205.80	$205.80
7 purchase totals =	$920.53		$1,009.5619	$1,009.55	$1,009.50	$1,009.50