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	$222.31	3.566%	$230.2376	$230.24	$230.25	$230.20
Purchase #2	$164.58	13.726%	$187.1703	$187.17	$187.15	$187.20
Purchase #3	$50.70	9.308%	$55.4192	$55.42	$55.40	$55.40
Purchase #4	$174.47	7.646%	$187.81	$187.81	$187.80	$187.80
Purchase #5	$158.68	10.458%	$175.2748	$175.27	$175.25	$175.30
Purchase #6	$130.80	7.413%	$140.4962	$140.50	$140.50	$140.50
Purchase #7	$113.85	11.805%	$127.29	$127.29	$127.30	$127.30
7 purchase totals =	$1,015.39		$1,103.6981	$1,103.70	$1,103.65	$1,103.70