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	$128.89	12.105%	$144.4921	$144.49	$144.50	$144.50
Purchase #2	$96.27	12.778%	$108.5714	$108.57	$108.55	$108.60
Purchase #3	$99.68	6.672%	$106.3306	$106.33	$106.35	$106.30
Purchase #4	$157.73	3.422%	$163.1275	$163.13	$163.15	$163.10
Purchase #5	$84.94	5.874%	$89.9294	$89.93	$89.95	$89.90
Purchase #6	$222.45	3.592%	$230.4404	$230.44	$230.45	$230.40
Purchase #7	$143.52	13.152%	$162.3958	$162.40	$162.40	$162.40
7 purchase totals =	$933.48		$1,005.2872	$1,005.29	$1,005.35	$1,005.20