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	$63.27	10.633%	$69.9975	$70.00	$70.00	$70.00
Purchase #2	$42.99	5.652%	$45.4198	$45.42	$45.40	$45.40
Purchase #3	$50.93	12.444%	$57.2677	$57.27	$57.25	$57.30
Purchase #4	$153.70	7.802%	$165.6917	$165.69	$165.70	$165.70
Purchase #5	$231.31	11.703%	$258.3802	$258.38	$258.40	$258.40
Purchase #6	$230.66	11.156%	$256.3924	$256.39	$256.40	$256.40
Purchase #7	$74.33	8.121%	$80.3663	$80.37	$80.35	$80.40
7 purchase totals =	$847.19		$933.5156	$933.52	$933.50	$933.60