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	$178.96	12.250%	$200.8826	$200.88	$200.90	$200.90
Purchase #2	$87.49	12.433%	$98.3676	$98.37	$98.35	$98.40
Purchase #3	$132.46	3.629%	$137.267	$137.27	$137.25	$137.30
Purchase #4	$129.70	10.588%	$143.4326	$143.43	$143.45	$143.40
Purchase #5	$230.30	4.835%	$241.435	$241.44	$241.45	$241.40
Purchase #6	$202.27	4.137%	$210.6379	$210.64	$210.65	$210.60
Purchase #7	$80.53	12.369%	$90.4908	$90.49	$90.50	$90.50
7 purchase totals =	$1,041.71		$1,122.5135	$1,122.52	$1,122.55	$1,122.50