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	$165.27	4.328%	$172.4229	$172.42	$172.40	$172.40
Purchase #2	$167.63	13.448%	$190.1729	$190.17	$190.15	$190.20
Purchase #3	$44.47	12.696%	$50.1159	$50.12	$50.10	$50.10
Purchase #4	$107.52	10.825%	$119.159	$119.16	$119.15	$119.20
Purchase #5	$47.85	11.630%	$53.415	$53.42	$53.40	$53.40
Purchase #6	$185.58	3.756%	$192.5504	$192.55	$192.55	$192.60
Purchase #7	$239.37	9.306%	$261.6458	$261.65	$261.65	$261.60
7 purchase totals =	$957.69		$1,039.4819	$1,039.49	$1,039.40	$1,039.50